Introduction to Stata 8

11.2. Continuous variables
oneway [R] oneway
compares means between two or more groups (analysis of variance):
oneway price type [ , tabulate noanova]
. oneway price type , tabulate
type of | Summary of price per 75 cl bottle
wine | Mean Std. Dev. Freq.
------------+------------------------------------
1. red | 48.15 12.650239 15
2. white | 42.590909 20.016952 11
3. rosé | 43.45 17.375268 6
4. undeterm | 59.616666 15.821924 3
------------+------------------------------------
Total | 46.58 16.304104 35
Analysis of Variance
Source SS df MS F Prob > F
------------------------------------------------------------------------
Between groups 780.660217 3 260.220072 0.98 0.4162
Within groups 8257.34954 31 266.366114
------------------------------------------------------------------------
Total 9038.00975 34 265.823816
Bartlett's test for equal variances: chi2(3) = 2.3311 Prob>chi2 = 0.507
The table, but not the test, could also be obtained by;
tabulate type , summarize(price) [R] tabsum
anova [R] anova
Similar to oneway, but handles a lot of complex situations.
tabstat [R] tabstat
tabstat is a flexible tool for displaying several types of tables, but includes no tests. To
obtain a number of descriptive statistics; here the mean, standard deviation, and 25, 50, and
75 percentiles:
.
tabstat price mpg weight , stat(n mean sd p25 p50 p75) col(stat) format(%8.2f)
variable | N mean sd p25 p50 p75
-------------+------------------------------------------------------------
price | 74.00 6165.26 2949.50 4195.00 5006.50 6342.00
mpg | 74.00 21.30 5.79 18.00 20.00 25.00
weight | 74.00 3019.46 777.19 2240.00 3190.00 3600.00
--------------------------------------------------------------------------
The col(stat) option let the statistics form the columns; without it the statistics would
have formed the rows. The format() option lets you decide the display format. The
statistics are:
n, mean, sum, min, max, range, sd, var, cv (coefficient of variation), semean, skew
(skewness), kurt (kurtosis), p1, p5, p10, p25, p50 (or median), p75, p90, p95, p99, q
(quartiles: p25, p50, p75), and iqr (interquartile range).
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