Question

5)

If you are conducting a within subjects design with two conditions and want 50 participants in each condition, how many participants total do you need? ANSWER

Given the mean of the difference scores is 7.0, standard deviation of the difference scores is 2.8, and there were 25 in the sample, solve for the following problems, showing all work to receive full credit:
6) Solve for the standard error of the difference scores:
Work:	Answer:
7) Calculate the correlated-groups t test to determine the tobt.
Work:	Answer:
8) If this is a non-directional test, what is the t cv?
(No work needed)	Answer:

Answer 1

5) Total participants we need = 50*2 =100

Note : Given 50 participants in each condition (group) and there are two conditions ( that is two groups) , thus total number of participants is 50*2= 100

6) Standard error of difference scores = standard deviation of difference in scores /

where n = sample size =25

standard deviation of difference in scores , = 2.8

thus , Standard error of difference scores =/ = 2.8 / = 0.56

7) Test statistic for paired t test ( correlated groups t test) is given by

Given ,

/ =0.56

Thus, t -obt = 7.0/0.56 = 12.5

t -obt = 12.5

8) We need to find critical value of t

Given , the test is non directional  , we need two tailed CV

Level of significance is not given , we assume

n= 25 , degrees of freedom = n-1 = 25-1 =24

From t table ,for with df =24 two tailed critical value of t is ,

t cv = + / - 2.064