Correct Hypothesis for Different Variances

1. A company has two different processes that make credit cards. Suspecting that machine B has a higher variability than machine A the manager orders a test to be run. The following data was collected:
Machine A Machine B
Sample size nA= 30 nB=40
Sample Standard Deviation sA= 1.0 sB= 1.7
a. Select the correct hypothesis to test for the difference in the variances.
1. 2.

3. 4.

b. What is the critical value of the F distribution?

c. Perform the test at the .05 level of significance. What is the observed value of the F distribution?

d. What are your conclusions?

2. The null hypothesis and the alternate are:
H0: The cell categories are equal
H1: The cell categories are not equal

Category Observed
A 10
B 20
C 30
Assume a significance level of 5%.
a. What is the critical value of the Chi-square?
b. Compute the observed value of Chi-square.
c. What is your decision regarding H0?

3. Complete the ANOVA summary table shown here.

Source of Variation Sum of Squares Degrees of freedom Mean Square F observed
Between Treatments
Error (Within Treatments)
Sums of Squares of Total

a. How many treatments are there?
b. What is the total sample size?
c. Is there a significant difference at the 5% Level of significance? Would I accept or reject the null Hypothesis. i.e. what is the critical value of the test statistic?

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