Question

Gueutal et al. (1995) tested the hypothesis that pregnancy would have an effect on performance appraisal ratings.   The data below has been shortened and simplified, but the results are similar to the original study.

We obtain a random sample of 7 female employees who are pregnant and 8 female employees who are not pregnant. Performance ratings were made on a scale from 1 (poor) to 7 (excellent).

	Pregnant	Not pregnant
N	7	8
Mean	5	3
SS	15	21
Variance	2.5	3

What is ?

What is the standard error of the mean difference  ?

Answer 1

Sample #1   ---->   sample 1
mean of sample 1,    x̅1=   5.00
standard deviation of sample 1,   s1 =    1.58
size of sample 1,    n1=   7
      
Sample #2   ---->   sample 2
mean of sample 2,    x̅2=   3.00
standard deviation of sample 2,   s2 =    1.73
size of sample 2,    n2=   8
      
pooled std dev , Sp=   √([(n1 - 1)s1² + (n2 - 1)s2²]/(n1+n2-2)) =    1.6641

std error , SE =    Sp*√(1/n1+1/n2) =    0.8613

..............................

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