1) Suppose you wish to construct a 98% confidence interval for a population mean. If the size of a sample is increases, but the sample mean and sample standard deviation remain the same, how is the margin of error the the 98% confidence interval affected?





A) The margin of error will become larger.

B) The margin of error will become smaller.

C) The margin of error will not change.

D) It is not possible to predict how the margin of error will be affected.





2)The rate of birth defects in the general population of 0.7% of all children born. A company that produces prenatal vitamins claims that the rate of birth defects in children born to women who use their prenatal vitamins is lower than normal. A sample of 2000 women who used the vitamins was selected and it was found that 0.45% of them gave birth to babies with birth defects. For the test conducted, the hypotheses are:



H0: p = 0.007 and HA: p < 0.007.



At a level of significance of 0.05, what is the probability of a Type I error? Explain briefly.



3) Suppose we are testing the hypotheses shown below. What is the p-value if t = -1.33 and the sample size is 9?



H0= mean of population =48.3 HA= mean of population < 48.3





3) The rate of birth defects in the general population is 0.4% of all children born. A group protesting the construction of a new power line claims that the rate of birth defects in children born to women who lived near major power lines during pregnancy is higher than normal. You wish to use a test of hypotheses to assess this claim. What should the null and alternative hypotheses be?



4) Nationally published statistics show that 4.9% of all free internet downloads are infected with viruses. A company that sells virus protection software claims that using its software will decrease the number of infected downloads you receive. A random sample of 1600 files was selected and downloaded using the software. Testing found that 4.12% of them were infected. For the test conducted, the hypotheses are:



H0: p = 0.049 and HA: p < 0.049.



Find the p-value for this test. (Round the answer to 4 decimal places.) What do you conclude?





5) Both Carson and Jamie wish to test that 7.4% of semi trucks on the road are past due for their safety inspections. Both take a sample of 700 trucks. Carson uses a significance level of 0.02 while Jamie uses a significance level of 0.01. Who is more likely to make a Type I error? Explain briefly.