Question

answer all these questions please with the right question number next to its letter

1-When the population standard deviation is unknown AND the sample size is less than 30, the test statistic to use is:

A		t
B		The Binomial Dristribution
C		The Z Distribution
D		Chi-Square

4-What do we call the statement (rule you create) that determines if the null hypothesis is rejected?

A		Decision rule
B		Test statistic
C		Alternate hypothesis
D		Critical mass

8-

The mean length of a small counter balance bar is 43 millimeters. There is concern that the adjustments of the machine producing the bars have changed. Test the claim at the 0.02 level that there has been no change in the mean length. The alternate hypothesis is that there has been a change. Twelve bars (n = 12) were selected at random and their lengths recorded. The lengths are (in millimeters) 42, 39, 42, 45, 43, 40, 39, 41, 40, 42, 43 and 42. The mean of the sample is 41.5 and the standard deviation 1.784. Computed t = – 2.913. Has there been a statistically significant change in the mean length of the bars (can we reject the null hypothesis HO)?

A		Yes, because the computed t lies in the area beyond the critical value.
B		No, because the information given is not complete.
C		No, because the computed t lies in the area to the right of –2.718.
D		None of the above

Answer 1

1 . Given

population standard deviation is unknown

the sample size is less than 30, the test statistic to use t test

if n < 30 use t test , n > = 30 use z test for large sample

Hence option A is correct

4. Decision rule determines whether the null hypothesis is rejected or not with the help of critical value rejection region

hence option A is correct

A

Decision rule

8. Given that

significance level = 0.02

claim : there is no change ( two tailed test because it means same )  

t = -2.913

critical value tc: