Need help with the attached Statistics worksheet.

Name __________________ Advance Univariate Statistics Psyc 541 Summer 2017 60 points

1. (6 points) What are the critical value or values for the following conditions(careful with the signs)

a) 1 tailed t test, df=20, α =.05                               b) 2 tailed t test, df=28 , α =.05 

H1 predicts decrease in the mean

c) 1 tailed z test, α =.05

H1 predicts an increase in the mean                                    d) 2 tailed z test, α =.05

e) 1 tailed t test, df=10, α =.01                                          f) 2 tailed t test, df=40, α =.01  

H1 predicts an increase in the mean

2. (3 points) Define each. Be very clear and precise

a) type 1 error -

b) power –

c) type 2 error -

3. (4 points) State the assumptions governing the use of a t-test of a difference between the means of two independent groups. Which of the assumptions is most important and under what conditions would violations of this assumption be especially severe.

4. (18 points) A psychologist finds that the number of employee errors increases as the day progresses, reaching a peak between 3:00 and 5:00 p.m. He divides a sample of 20 employees into two groups. One group proceeds on the same work schedule as before, but the other group takes a 15-minute coffee break from 2:45 to 3:00. The subsequent number of errors made between 3:00 and 5:00 are listed below.

No Break Group        5         6         7         4         8         9         6         5         7         6

Break Group             2         3         4         3         4         4         3         1         5         4

No Break        ∑ X =            ∑ X² =                                    Break              ∑ X =            ∑ X² =

State the null hypothesis.

State the alternative 2 tailed hypothesis. Use alpha=.05       

Compute the appropriate t-test.(list all the components of each SS and then the final answer)

SS1=                                                                         SS2=

T=

State the critical t needed for significance. (careful with the signs)

Compute omega squared.      

Compute the appropriate Cohen’s d                                    

State your conclusions.

Calculate the 95% confidence interval for the observed difference between the two means.

. (20 points) A company has just switched to a 4-day work week. It has measured the number of units produced per week for 10 employees before and after the change. Does the change impact production.

           Employee            Before              After                             

                       A                    25                   23       

                       B                    26                   24       

                       C                    27                   26                   ∑ D =

                       D                    22                   19       

                       E                     29                   30       

                       F                     25                   24                   ∑ D2  =

                       G                    29                   22       

                       H                    30                   32       

                       I                      25                   23       

                       J                      28                   21       

Does changing the workweek influence sales? Use α =.05               2 tailed.

State the null hypothesis.       

State the alternative hypothesis.        

Compute the appropriate t-test.

SSd =

SSd=

T=

State the critical t needed for significance (careful with the signs).

State your conclusions.

.

What would your conclusions be if you used the sign test and why?

6. ( 2 points) Describe in words the two steps involved in the calculation of power.

7. (3 points) Describe why we never “accept” the null hypothesis and what relationship this has to power. (be complete

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