n1=28
mean1=72.75
SD1=5.37225
n1=24
mean1=72.625
SD1=7.69987
Im finding a 90% confidence interval of the difference.
What is the df?
What is the t*?
I dont get it.
Are the samples independent? I'll assume that they are.
The samples are small size so the t-distribution should be used. Since and do NOT differ by an order of magnitude, it can be assumed that df =
.
Two tailed therefore require (refer table given at Student's t-distribution - Wikipedia, the free encyclopedia or use the calculator found at http://www.anu.edu.au/nceph/surfstat...e/tables/t.php).
The confidence interval is
Since the degree of freedom is so large you could use the z-distribution without too much error.