Question

A recent study of two vendors of desktop personal computers reported that out of 895 units sold by Brand A, 118 required repair, while out of 711 units sold by Brand B, 98 required repair. Round all numeric answers to 4 decimal places.

1. Calculate the difference in the sample proportion for the two brands of computers, ?̂ ??????−?̂ ??????p^BrandA−p^BrandB =  .

2. What are the correct hypotheses for conducting a hypothesis test to determine whether the proportion of computers needing repairs is different for the two brands.

A. ?0:??−??=0H0:pA−pB=0, ??:??−??<0HA:pA−pB<0
B. ?0:??−??=0H0:pA−pB=0, ??:??−??≠0HA:pA−pB≠0
C. ?0:??−??=0H0:pA−pB=0, ??:??−??>0HA:pA−pB>0

3. Calculate the pooled estimate of the sample proportion, ?̂ p^ =

4. Is the success-failure condition met for this scenario?

A. Yes
B. No

5. Calculate the test statistic for this hypothesis test.  ? z t X^2 F  =

6. Calculate the p-value for this hypothesis test, p-value =  .

7. Based on the p-value, we have:
A. little evidence
B. strong evidence
C. some evidence
D. very strong evidence
E. extremely strong evidence
that the null model is not a good fit for our observed data.

8. Compute a 99 % confidence interval for the difference ?̂ ??????−?̂ ??????p^BrandA−p^BrandB = (  ,  )

Answer 1

4. Is the success-failure condition met for this scenario? YES

7. Based on the p-value, we have: A. little evidence that the null model is not a good fit for our observed data.