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2011 National Survey of Fishing, Hunting, and ... - Census Bureau

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generalized variance function are estimated using direct replicate variances. These generalized variance parameters provide a<br />

relatively easy method to obtain approximate st<strong>and</strong>ard errors for numerous characteristics. Table D-2 provide the generalized<br />

variance parameters for FHWAR data. Methods for using the parameters to calculate st<strong>and</strong>ard errors <strong>of</strong> various estimates are<br />

given in the next sections.<br />

St<strong>and</strong>ard St<strong>and</strong>ard Errors Errors <strong>of</strong> Estimated <strong>of</strong> Estimated Numbers. Numbers. The approximate The approximate st<strong>and</strong>ard st<strong>and</strong>ard error, sx error, , <strong>of</strong> an sx<br />

, estimated <strong>of</strong> an estimated number number shown shown in this in report this report can can<br />

St<strong>and</strong>ard be Errors obtained be obtained <strong>of</strong> Estimated using the using following Numbers. the following formulas. The approximate formulas. Formula Formula st<strong>and</strong>ard (1) is used (1) error, is to used scalculate x<br />

, <strong>of</strong> to an calculate estimated the st<strong>and</strong>ard the number st<strong>and</strong>ard errors shown errors <strong>of</strong> levels in <strong>of</strong> this levels <strong>of</strong> sportspersons,<br />

report <strong>of</strong> sportspersons,<br />

can be obtained anglers, St<strong>and</strong>ard anglers, using wildlife-watchers.<br />

Errors <strong>and</strong> the following wildlife-watchers.<br />

<strong>of</strong> Estimated formulas. Numbers. Formula The (1) approximate is used to calculate st<strong>and</strong>ard the error, st<strong>and</strong>ard errors <strong>of</strong> levels <strong>of</strong> sportspersons,<br />

anglers, <strong>and</strong> wildlife watchers.<br />

sx<br />

, <strong>of</strong> an estimated number shown in this report can<br />

be obtained using the following formulas. Formula (1) is used to calculate the st<strong>and</strong>ard errors <strong>of</strong> levels <strong>of</strong> sportspersons,<br />

anglers, <strong>and</strong> wildlife-watchers.<br />

s <br />

2<br />

s <br />

2<br />

ax ax <br />

(1)<br />

bx<br />

(1)<br />

(1)<br />

x<br />

bx<br />

x<br />

2<br />

Here, x Here, is the x Here, size is the <strong>of</strong> x the size is the estimate <strong>of</strong> size the <strong>of</strong> estimate <strong>and</strong> the a estimate <strong>and</strong> <strong>and</strong> b a are <strong>and</strong> the b a parameters are <strong>and</strong> the b are parameters the in parameters the tables in the associated in tables the tables associated with associated the with particular the with particular the characteristic.<br />

(1)<br />

particular characteristic. characteristic.<br />

Formula Formula (2) Here, is Formula used (2) x is for is the used (2) st<strong>and</strong>ard size is for used <strong>of</strong> st<strong>and</strong>ard the errors for estimate st<strong>and</strong>ard <strong>of</strong> errors aggregates, <strong>and</strong> errors <strong>of</strong> a aggregates, <strong>and</strong> <strong>of</strong> i.e., b aggregates, are trips, the i.e., days, parameters trips, i.e., <strong>and</strong> days, trips, expenditures. in <strong>and</strong> days, the expenditures. tables <strong>and</strong> expenditures. associated with the particular characteristic.<br />

Formula (2) is used for st<strong>and</strong>ard errors <strong>of</strong> 2<br />

s 2 cx<br />

s aggregates,<br />

ax i.e.,<br />

ax bx<br />

<br />

trips,<br />

2<br />

bx <br />

days, <strong>and</strong> expenditures.<br />

2<br />

x<br />

(2)<br />

x<br />

(2)<br />

y 2y<br />

(2)<br />

s 2<br />

ax bx cx<br />

x<br />

(2)<br />

Here, x Here, is again x Here, is the again x size is the again <strong>of</strong> the size the estimate; <strong>of</strong> size the <strong>of</strong> estimate; y the is the estimate; base y is the <strong>of</strong> y the base is the estimate; <strong>of</strong> base the <strong>of</strong> estimate; <strong>and</strong> the a, estimate; yb, <strong>and</strong> <strong>and</strong> a, c <strong>and</strong> b, are <strong>and</strong> a, the b, c parameters are <strong>and</strong> the c are parameters the in parameters the tables in the associated<br />

with ated the with particular ated the with particular the characteristic. particular characteristic. characteristic.<br />

in tables the tables associ-<br />

associ-<br />

Here, x is again the size <strong>of</strong> the estimate; y is the base <strong>of</strong> the estimate; <strong>and</strong> a, b, <strong>and</strong> c are the parameters in the tables associated<br />

<strong>of</strong> Illustration the with Computation <strong>of</strong> the the particular <strong>of</strong> Computation the Computation <strong>of</strong> characteristic. the St<strong>and</strong>ard <strong>of</strong> the <strong>of</strong> St<strong>and</strong>ard the Error St<strong>and</strong>ard <strong>of</strong> Error Estimated Error <strong>of</strong> an Estimated <strong>of</strong> an Number Estimated Number Illustration Illustration Number<br />

Suppose Table there Illustration 1 Table were in this 1 an in report estimated <strong>of</strong> this the report shows Computation 37,397,000 shows that 33,916,000 that persons <strong>of</strong> 33,916,000 the persons St<strong>and</strong>ard age 16 persons 16 years Error years 16 old old years <strong>of</strong> <strong>and</strong> <strong>and</strong> older Estimated older <strong>and</strong> who either older either Number either fished fished fished or or hunted hunted or hunted in in the the in United United the United States States in in<br />

States in 2006. <strong>2011</strong>. 2006. Using Using formula formula (1) (1) with (1) the the with parameters the parameters a a = -0.000027 –0.000070 a = -0.000027 <strong>and</strong> <strong>and</strong> b b = <strong>and</strong> = 6,125 16,823 b = 6,125 from from table from table D-7, table D-2, the D-7, the approximate the approximate st<strong>and</strong>ard st<strong>and</strong>ard<br />

error the <strong>of</strong> estimate Table the estimated 1 in number this report number <strong>of</strong> 33,916,000 shows <strong>of</strong> <strong>of</strong> 33,916,000 37,397,000 that sportspersons 33,916,000 sportspersons persons 16 years 16 age old years 16 <strong>and</strong> years old older <strong>and</strong> old is<br />

older <strong>and</strong> older is either is fished or hunted in the United States in<br />

st<strong>and</strong>ard error <strong>of</strong> error <strong>of</strong><br />

2006. Using formula (1) with the parameters a = -0.000027 <strong>and</strong> b = 6,125 from table D-7, the approximate st<strong>and</strong>ard error <strong>of</strong><br />

2<br />

the estimate number <strong>of</strong> 33,916,000 sportspersons 16 years old<br />

2<br />

<strong>and</strong> older is<br />

s x<br />

s x<br />

0 . 000027 0. 000027 33, 916 33, 000 , 916, 000 6, 125 6, 125 33, 916 33, 000 , 916, 000 420,<br />

330 420,<br />

330<br />

The 95-percent The 95-percent The confidence 95-percent confidence interval confidence interval for the interval estimated for the for estimate the number estimate number <strong>of</strong> sportspersons number <strong>of</strong> 2<br />

s<br />

sportspersons <strong>of</strong> sportspersons 16 years 16 old years 16 <strong>and</strong> old years older <strong>and</strong> old is older from <strong>and</strong> is older 35,968,000 from is 33,092,000 from to 33,092,000 to to<br />

38,826,000, 34,740,000, i.e., 34,740,000, 37,397,000 ie., 33,916,000 ie., ± 33,916,000 x<br />

0. 000027 33, 916, 000 6, 125 33, 916, 000 420,<br />

330<br />

1.96 ± x 728,857. 1.96 ± x 1.96 420,330. Therefore, x 420,330. Therefore, a conclusion Therefore, a conclusion that a conclusion the that average the that average estimate the average estimate derived estimate derived from all derived from possible all from possible all possible<br />

samples samples lies The within samples 95-percent lies a within range lies within confidence a computed range a range computed interval this computed way in for this would the in way estimate this be would way correct number would correct for be roughly <strong>of</strong> correct sportspersons for roughly 95 for percent roughly 9516 percent <strong>of</strong> years 95 all percent possible old <strong>of</strong> all <strong>and</strong> possible <strong>of</strong> samples. older all possible is samples. from samples. 33,092,000 to<br />

34,740,000, ie., 33,916,000 ± 1.96 x 420,330. Therefore, a conclusion that the average estimate derived from all possible<br />

Suppose Table there samples 1 Table were shows 1 lies an shows that estimated within 12,510,000 that a range 12,510,000 13,674,000 hunters computed hunters 16 in years this 16 age old years way 16 <strong>and</strong> years would old older <strong>and</strong> old be engaged older <strong>and</strong> correct older engaged in for who 219,925,000 roughly in engaged 219,925,000 95 percent in days 281,884,000 <strong>of</strong> days <strong>of</strong> participation all <strong>of</strong> possible participation days <strong>of</strong> in samples. participation<br />

in formula <strong>2011</strong>. formula Using (2) with formula (2) the with parameters (2) the with parameters the a = parameters -0.000235, a = -0.000235, a b = –0.000284, -85,241, b = -85,241, <strong>and</strong> b = c = –127,863, <strong>and</strong> 22,698 c = 22,698 from <strong>and</strong> c table from = 46,699 D-9, table the from D-9, approximate table the approximate D-2, the st<strong>and</strong>ard st<strong>and</strong>ard error on error on<br />

2006. in 2006. Using Using<br />

approximate 219,925,000 Table st<strong>and</strong>ard 219,925,000 1 shows estimated error that estimated on 12,510,000 281,884,000 days on days an estimated on hunters estimated an estimated 16 base years days <strong>of</strong> base on old 12,510,000 <strong>and</strong> <strong>of</strong> estimated 12,510,000 older hunters engaged base hunters is <strong>of</strong> in 13,674,000 219,925,000 is hunters days <strong>of</strong> is participation in 2006. Using<br />

formula (2) with the parameters a = -0.000235, b = -85,241, <strong>and</strong> c = 22,698 from table D-9, the approximate st<strong>and</strong>ard error on<br />

2<br />

219,925,000 estimated days on an estimated base <strong>of</strong> 12,510,000 hunters is<br />

2<br />

2<br />

22, 698 22<br />

2<br />

, 698 219<br />

, 925 219,<br />

000 , 925,<br />

000<br />

s x<br />

s x<br />

0 . 000235 0. 000235 219, 925 219, 000 , 925, 000 85, 241 85, 241 219, 925 219,<br />

000 , 925,<br />

000 <br />

7, 592 7,<br />

000 , 592,<br />

000<br />

12, 510 12,<br />

000 , 510,<br />

000 2<br />

2<br />

22, 698 219, 925,<br />

000<br />

s x<br />

0. 000235 219, 925, 000 85, 241 219, 925,<br />

000 <br />

7, 592,<br />

000<br />

12, 510,<br />

000<br />

The 95-percent The 95-percent confidence confidence interval interval on the on estimate the estimate <strong>of</strong> 219,925,000 <strong>of</strong> 219,925,000 days is days from is 205,044,000 from 205,044,000 to 234,806,000, to 234,806,000, ie., 219,925,000 ie., 219,925,000<br />

± 1.96 ± x 1.96 7,592,000. x 7,592,000. Again, Again, a conclusion a conclusion that the that average the average estimate estimate derived derived from all from possible all possible samples samples lies within lies within a range a range<br />

The 95-percent computed The computed confidence 95-percent in this in way this confidence interval would way would be interval the correct estimate be correct on for the roughly <strong>of</strong> for estimate 281,884,000 roughly 95 percent <strong>of</strong> 95 219,925,000 days percent <strong>of</strong> is all from possible <strong>of</strong> days all 253,295,000 possible is samples. from samples. 205,044,000 to 310,473,000, to 234,806,000, i.e., ie., 219,925,000<br />

281,884,000 ± ± 1.96 1.96 x x 7,592,000. 14,586,000. Again, Again, a conclusion a that that the the average estimate derived from from all all possible samples lies lies within within a range<br />

a range St<strong>and</strong>ard computed computed St<strong>and</strong>ard Errors in this in Errors this <strong>of</strong> way Estimated way would <strong>of</strong> Estimated would be Percentages. correct be correct Percentages. for for roughly The roughly reliability The 95 reliability percent 95 percent <strong>of</strong> an <strong>of</strong> estimated <strong>of</strong> all <strong>of</strong> an possible all estimated possible percentage, samples. percentage, samples. computed computed using sample using sample data for data both for both<br />

numerator numerator <strong>and</strong> denominator, <strong>and</strong> denominator, depends depends on the on size the <strong>of</strong> size the <strong>of</strong> percentage the percentage <strong>and</strong> its <strong>and</strong> base. its base. Estimated Estimated percentages percentages are relatively are relatively more more<br />

St<strong>and</strong>ard reliable Errors St<strong>and</strong>ard reliable than <strong>of</strong> Estimated the Errors than corresponding the <strong>of</strong> Percentages. corresponding Estimated estimates Percentages. The estimates reliability <strong>of</strong> the The <strong>of</strong> numerators the <strong>of</strong> reliability an numerators estimated <strong>of</strong> <strong>of</strong> the an <strong>of</strong> percentages, percentage, estimated the percentages, percentage, computed particularly particularly using computed if the sample percentages if the using data percentages sample for are both 50 data are percent 50 for percent both<br />

numerator more. <strong>and</strong> numerator denominator, more. When <strong>and</strong> When the denominator, numerator depends the numerator on <strong>and</strong> depends the the <strong>and</strong> size denominator the <strong>of</strong> on the denominator percentage size <strong>of</strong> <strong>of</strong> the the <strong>of</strong> percentage <strong>and</strong> the its percentage base. are <strong>and</strong> Estimated in its are different base. in different percentages Estimated categories, categories, percentages are use relatively the use parameter the are more parameter relatively in the more in the<br />

reliable tables than reliable the tables indicated corresponding than indicated by the the corresponding by numerator. estimates the numerator. <strong>of</strong> estimates the numerators <strong>of</strong> the numerators <strong>of</strong> the percentages, <strong>of</strong> the percentages, particularly particularly if the percentages if the percentages are 50 percent are 50 percent<br />

or more. When or more. the numerator When the <strong>and</strong> numerator the denominator <strong>and</strong> the denominator <strong>of</strong> the percentage <strong>of</strong> the are percentage in different are categories, in different use categories, the parameter use the in parameter the in the<br />

tables indicated The tables approximate The by indicated approximate the numerator. st<strong>and</strong>ard by the st<strong>and</strong>ard error, numerator. serror, x,p,<br />

can s x,p,<br />

be can obtained be obtained by use by <strong>of</strong> use the <strong>of</strong> formula the formula<br />

The approximate The approximate st<strong>and</strong>ard error, st<strong>and</strong>ard s x,p<br />

, can error, be obtained s x,p,<br />

can be by obtained use <strong>of</strong> the by formula use <strong>of</strong> the formula<br />

s<br />

x,<br />

p<br />

s ax bx<br />

s<br />

,p<br />

x <br />

s<br />

,p<br />

bp( 100 bp( 100 p)<br />

p)<br />

,p<br />

,<br />

<br />

bp<br />

x<br />

( 100x<br />

p)<br />

<br />

x p<br />

Here, x Here, is the x total is the number total number <strong>of</strong> sportspersons, <strong>of</strong> sportspersons,<br />

x,<br />

phunters, hunters, etc., which etc., which is the base is the <strong>of</strong> base the <strong>of</strong> percentage; the percentage; p is the p percentage is the percentage<br />

(3)<br />

x<br />

(3) (0 ≤ p (0 ≤ ≤ p ≤<br />

100); <strong>and</strong> 100); b is <strong>and</strong> the b parameter is the parameter in the in tables the tables associated associated with the with characteristic the characteristic in the in numerator the numerator <strong>of</strong> the <strong>of</strong> percentage. the percentage.<br />

Here, x is the Here, total x number is the total <strong>of</strong> sportspersons, number <strong>of</strong> sportspersons, hunters, etc., hunters, which etc., is the which base <strong>of</strong> is the percentage; base <strong>of</strong> the percentage; p is the percentage; p is the percentage <strong>and</strong> b is the (0 ≤ p ≤<br />

parameter Illustration in 100); the Illustration tables <strong>and</strong> <strong>of</strong> b the associated is the <strong>of</strong> Computation the parameter Computation with the in <strong>of</strong> the characteristic the tables <strong>of</strong> St<strong>and</strong>ard the associated St<strong>and</strong>ard in Error the numerator with Error <strong>of</strong> an the Estimated <strong>of</strong> characteristic <strong>of</strong> an the Estimated percentage. Percentage in the Percentage numerator <strong>of</strong> the percentage.<br />

Table Illustration 1 Table shows 1 shows that <strong>of</strong> <strong>of</strong> the that the Computation <strong>of</strong> 12,510,000 the 12,510,000 hunters <strong>of</strong> the hunters St<strong>and</strong>ard 16 years 16 old years Error <strong>and</strong> old <strong>of</strong> older, <strong>and</strong> Estimated older, 18.3 percent 18.3 Percentage percent hunted hunted migratory migratory birds. birds. From table From D-7, table D-7,<br />

the appropriate the appropriate b parameter b parameter is 5,756. is 5,756. Using Using formula formula (3), the (3), approximate the approximate st<strong>and</strong>ard st<strong>and</strong>ard error on error the on estimate the estimate <strong>of</strong> 18.3 <strong>of</strong> percent 18.3 percent is is<br />

68 <strong>2011</strong> <strong>National</strong> <strong>Survey</strong> <strong>of</strong> <strong>Fishing</strong>, <strong>Hunting</strong>, <strong>and</strong> Wildlife-Associated Recreation—Vermont U.S. Fish <strong>and</strong> Wildlife Service <strong>and</strong> U.S. <strong>Census</strong> <strong>Bureau</strong><br />

Table 1 shows that <strong>of</strong> the 12,510,000 hunters 16 years old <strong>and</strong> older, 18.3 percent hunted migratory birds. From table D-7,<br />

the appropriate b parameter is 5,756. Using formula (3), the approximate st<strong>and</strong>ard error on the estimate <strong>of</strong> 18.3 percent is<br />

cx<br />

(3)<br />

(3)

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