Problem 8.1, page 159 from Zar (1999)
Output from SigmaStat

t-test                          Wednesday, September 27, 2000, 15:11:53

Normality Test:	Passed	(P = 0.319)

Equal Variance Test:	Passed	(P = 0.384)

Group     N    Missing	
males     7      0	
females   6      0	

Group     Mean    Std Dev    SEM	
males   224.271    4.211    1.592	
females 225.667    3.867    1.579	

Difference	-1.395

t = -0.618  with  11 degrees of freedom. (P = 0.549)

 95 percent confidence interval for difference of means: -6.364 to 3.574

The difference in the mean values of the two groups is not great enough
to reject the possibility that the difference is due to random sampling
variability. There is not a statistically significant difference between
the input groups (P = 0.549).

Power of performed test with alpha = 0.050: 0.050

The power of the performed test (0.050) is below the desired power of 0.800.
You should interpret the negative findings cautiously.



Problem 8.2, page 159 from Zar (1999)
Output from SigmaStat

t-test	                           Wednesday, September 27, 2000, 15:14:43

Normality Test:	Passed	(P = 0.826)

Equal Variance Test:	Passed	(P = 0.310)

Group         N     Missing	
northern      7        0	
southern      8        0	

Group        Mean      Std Dev      SEM	
northern    117.857     4.059      1.534	
southern    118.125     2.997      1.060	

Difference	-0.268

t = -0.147  with  13 degrees of freedom. (P = 0.886)

 95 percent confidence interval for difference of means: -4.212 to 3.676

The difference in the mean values of the two groups is not great enough to
reject the possibility that the difference is due to random sampling
variability. There is not a statistically significant difference between
the input groups (P = 0.886).

Power of performed test with alpha = 0.050: 0.050

The power of the performed test (0.050) is below the desired power of 0.800.
You should interpret the negative findings cautiously.
Return to the notes for Chapter 8
Last updated on 26 September 2000.
Provide comments to Dwight Moore at mooredwi@emporia.edu.
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