Stats Final

A large utility company wants to explore whether they can predict electrical consumption for their residential customers using size of their residence. The manager of the company predicted the electrical consumption for a 2200 square foot residence to be ŷ= 74.4 kilowatts. ----- Suppose the 95% confidence interval for the mean electrical consumption is (68.7, 80.1). Which of the following is a correct interpretation of this confidence interval?

A large utility company wants to explore whether they can predict electrical consumption for their residential customers using size of their residence. The manager of the company predicted the electrical consumption for a 2200 square foot residence to be ŷ= 74.4 kilowatts. ----- Suppose the 95% confidence interval for the mean electrical consumption is (68.7, 80.1). Which of the following is a correct interpretation of this confidence interval? -- Suppose the 95% prediction interval for an individual residence’s electrical consumption is (67.3 , 81.5). Which of the following is a correct interpretation of this prediction interval?

Suppose a 95% confidence interval for the mean tail length of all giant pandas who weigh 110 kilograms is (12.32 cm, 13.88 cm). Which of the following could be the corresponding 95% prediction interval for the tail length of an individual giant panda who weighs 110 kilograms? (Hint: ŷ = 13.1)

A consumer testing service tested whether the average baking time of whole wheat bread in gas ovens was less than the average baking time of whole wheat bread in electric ovens. Ten loaves of whole wheat bread were prepared and five were randomly assigned to be baked in the five randomly selected gas ovens and five were randomly assigned to be baked in the five randomly selected electric ovens. -- Which procedure should be used for this test?

A poultry specialist is conducting an experiment to determine whether the mean cholesterol content of egg yolks is affected by adding certain chemicals to the feed given to the hens laying those eggs. The 120 laying hens available for the study will be randomly allocated to three groups. Each group of hens will be fed a ration with a different chemical additive and the cholesterol content of their eggs measured. -- Which procedure should be used for this test?

If all possible samples of size 20 are taken instead of size 100, how would this change the mean and standard deviation of the sampling distribution of x̄?

Scores on the math portion of the SAT follow a Normal distribution with a mean of 507 and a standard deviation of 111. --What is the probability that the mean SAT math score of a sample of 4 students is more than 600?

Scores on the math portion of the SAT follow a Normal distribution with a mean of 507 and a standard deviation of 111. --What is the probability that any random sample of 4 students has an average SAT math score between 400 and 625?

A professor reported that students in a class had a mean score of 81.9 and a standard deviation of 6.1 on the final exam. A student took a random sample of 50 students and calculated the mean score to be 80.3. What is the probability that this student would get a mean of 80.3 or lower?

The weights of Cougar Tail donuts are known to have a normal distribution with a mean of 5.78 oz and a standard deviation of .21. -- What is the chance that a random sample of 10 donuts has a mean weight that is less than 5.6 oz?

For many years, "working full-time" has meant working 40 hours per week. Nowadays it seems that corporate employers expect their employees to work more than this amount. A researcher decides to investigate this hypothesis. The null hypothesis states that the average time full-time corporate employees work per week is 40 hours. The alternative hypothesis states that the average time full-time corporate employees work per week is more than 40 hours. To substantiate his claim, the researcher randomly selected 40 corporate employees and finds that they work an average of 43 hours per week with a standard deviation of 9.6 hours. --- What is the test statistic for testing the hypotheses H0: μ =40 vs. Ha: μ > 40?

For many years, "working full-time" has meant working 40 hours per week. Nowadays it seems that corporate employers expect their employees to work more than this amount. A researcher decides to investigate this hypothesis. The null hypothesis states that the average time full-time corporate employees work per week is 40 hours. The alternative hypothesis states that the average time full-time corporate employees work per week is more than 40 hours. To substantiate his claim, the researcher randomly selected 40 corporate employees and finds that they work an average of 43 hours per week with a standard deviation of 9.6 hours. Suppose the test statistic is 1.37. -- What is the p-value for this one-sided test?

An article claims that teenagers on average will check their cellphones 150 times in one day. A student decides to test this claim using the hypotheses H0: μ = 150 vs. Ha: μ ≠ 150. A 95% confidence interval for the true mean is found to be (154.3, 167.5). On the basis of this interval, what should the student conclude at α=0.05?

True or False: Statistically significant means that there is enough evidence to think that two groups do not have the exact same result, whereas practical significance can only be determined by the researcher if the results are worth acting upon.

True or False: If the population proportion is 0.04, the sampling distribution of p̂ for samples of size 100 will be approximately Normal.

In 2012, 21% of BYU undergraduates were married. Using a sample size of 200, what is the mean of the sampling distribution of p̂?

In 2012, 21% of BYU undergraduates were married. Using a sample size of 200. If we took samples of size 100 instead of 200, what would the mean of the sampling distribution of p̂ be?

Fill in the blank: The standard deviation of the sampling distribution of p̂ for samples of size 100 is _________ the standard deviation for samples of size 200.

In 2012, 21% of BYU undergraduates were married. Using a sample size of 200 --What is the probability of getting a sample proportion, p̂, from an SRS of 100 BYU undergraduates between 0.18 and 0.28?