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Biostatistics

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7.5 HYPOTHESIS TESTING: A SINGLE POPULATION PROPORTION 259<br />

7. Calculation of test statistic.<br />

:080 :063<br />

z ¼ rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi<br />

¼ 1:21<br />

ð:063Þ ð:937Þ<br />

301<br />

8. Statistical decision. Do not reject H 0 since 1:21 < 1:645.<br />

9. Conclusion. We cannot conclude that in the sampled population the<br />

proportion who are IFG is higher than 6.3 percent.<br />

10. p value. p ¼ :1131. &<br />

Tests involving a single proportion can be carried out using a variety of computer<br />

programs. Outputs from MINITAB and NCSS, using the data from Example 7.5.1, are<br />

shown in Figure 7.5.1. It should be noted that the results will vary slightly, because of<br />

rounding errors, if calculations are done by hand. It should also be noted that some<br />

programs, such as NCSS, use a continuity correction in calculating the z-value, and<br />

therefore the test statistic values and corresponding p values differ slightly from the<br />

MINITAB output.<br />

MINITAB Output<br />

Test and CI for One Proportion<br />

Test of p 0.063 vs p 0.063<br />

95% Lower<br />

Sample X N Sample p Bound Z-Value P-Value<br />

1 24 301 0.079734 0.054053 1.19 0.116<br />

Using the normal approximation.<br />

NCSS Output<br />

Normal Approximation using (P0)<br />

Alternative Z-Value Prob Decision<br />

Hypothesis<br />

Level<br />

(5%)<br />

P P0 1.0763 0.281780 Accept H0<br />

P P0 1.0763 0.859110 Accept H0<br />

P P0 1.0763 0.140890 Accept H0<br />

FIGURE 7.5.1 MINITAB and partial NCSS output for the data in Example 7.5.1.

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