# A random sample of healthy residents has a mean chloride

A laboratory in New York is interested in finding the mean chloride level for a healthy resident in the state. A random sample of healthy residents has a mean chloride level of mEq/L. If it is known that the chloride levels in healthy individuals residing in New York have a standard deviation of mEq/L, find a confidence interval for the true mean chloride level of all healthy New York residents. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. (If necessary, consult a list of formulas.) What is the lower level of the 95% confidence interval? What is the upper level of the 95% confidence interval?70 healthy residence 105 mEq/L mean 42 mEq/L standard deviation 95% confidence interval

2) Many college graduates who are employed full-time have longer than 40 hour work weeks. Suppose that we wish to estimate the mean number of hours, , worked per week by college graduates employed full-time. Well choose a random sample of college graduates employed full-time and use the mean of this sample to estimate . Assuming that the standard deviation of the number of hours worked by college graduates is 6.10 hours per week, what is the minimum sample size needed in order for us to be 95% confident that our estimate is within 1.5 hours per week of ?Carry your intermediate computations to at least three decimal places. Write your answer as a whole number (and make sure that it is the minimum whole number that satisfies the requirements).3) A researcher collected sample data for 15 women ages 18 to 24. The sample had a mean serum cholesterol level (measured in mg/100 mL) of 191, with a standard deviation of 5.3. Assuming that serum cholesterol levels for women ages 18 to 24 are normally distributed, find a 90% confidence interval for the mean serum cholesterol level of all women in this age group. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

what is the lower limit of the confidence interval, and the upper limit?

4) A furniture store claims that a specially ordered product will take, on average, A furniture store claims that a specially ordered product will take, on average, = 42 days (6 weeks) to arrive. The standard deviation of these waiting times is 7 days. We suspect that the special orders are taking longer than this. To test this suspicion, we track a random sample of 40 special orders and find that the orders took a mean of 44 days to arrive. Assume that the population is normally distributed. Can we conclude at the 0.1 level of significance that the mean waiting time on special orders at this furniture store exceeds 42 days?

Perform a one-tailed test. Then fill in the table below. Carry your intermediate computations to at least three decimal places, and round your responses as specified in the table. The table asks for: 1. Null hypothesis 2. Alternative hypothesis 3. Test statistic (z,t,chi square, or f) 4. Value of test statistic (Round to at least 3 dec. places

What is the critical value at the 0.1 level of significance (round to at least 3 decimals. Can we conclude that the mean waiting time on special orders at this furniture store exceeds 42 days? Yes or no

5) Loretta, who turns 91 this year, has heard that the mean systolic blood pressure among the elderly is 120 millimeters of mercury (mmHg), but she believes that the actual value is higher. She bases her belief on a recently reported study of 18 randomly selected, elderly adults. The sample mean systolic blood pressure of the adults in the study was 130 mmHg, and the sample standard deviation was 24 mmHg.

Assume that the population of systolic blood pressures of elderly adults is normally distributed. Based on the study, at the 0.1 level of significance, can it be concluded that (mu) , the mean systolic blood pressure among elderly adults, is greater than 120 mmHg? Perform a one-tailed test. Then fill in the table below. Carry your intermediate computations to at least three decimal places and round your answers as specified in the table.

Is critical value the same as P-value? And the test statistic t is asking for degrees of freedom. What would that be?

6) A presidential candidates aide estimates that, among all college students, the proportion p who intend to vote in the upcoming election is at least 60%. If 126 out of a random sample of 240 college students expressed an intent to vote, can we reject the aides estimate at the .05 level of significance?Perform a one-tailed test. Then fill in the table below. Carry your intermediate computations to at least three decimal places and round your answers as specified in the table. 1. null hypothesis 2. alternative hypothesis 3. type of test statistic 4. value of test statistic (round to 3 dec.) 5. critical value 6. can we reject the aids estimate that the proportion of college students who intend to vote is at least 60%?7) A study conducted by the research department of a pharmaceutical company claims that the annual spending (per person) for prescription drugs for allergy relief, (mu1) , is greater than or equal to the annual spending (per person) for non-prescription allergy relief medicine,(mu2) . A health insurance company conducted an independent study and collected data from a random sample of 295 individuals for prescription allergy relief medicine. The sample mean is found to be 17.7 dollars/year, with a sample standard deviation of 5.1 dollars/year. They have also collected data for non-prescription allergy relief medicine. An independent random sample of 205 individuals yielded a sample mean of 18.3 dollars/year, and a sample standard deviation of 4.6 dollars/year. Since the sample size is quite large, it is assumed that the population standard deviation of the sales (per person) for prescription and non-prescription allergy relief medicine can be estimated by using the sample standard deviation values given above. Is there sufficient evidence to reject the claim made by the research department of the company, at the .05 level of significance? Perform a one-tailed test. Then fill in the table below.

Carry your intermediate computations to at least three decimal places and round your answers as specified in the table. 1. null 2. alternative 3. test statistic (w/degrees of freedom if neces. 4. value of test stat. (round 3 dec) 5. critical value at .05 level of sig. 6. Can we reject the claim that the mean spending on prescription allergy medicine is greater than or equal to mean spending on non-prescription?

8) A purchasing manager for a large university is investigating which brand of LCD projector to purchase to equip smart classrooms. Of major concern is the longevity of the light bulbs used in the projectors. The purchasing manager has narrowed down the choice of projector to two brands, Infocus and Proxima, and wishes to determine if there is any difference between the two brands in the mean lifetime of the bulbs used.The purchasing manager obtained twelve projectors of each brand for testing over the last several academic terms. The number of hours the bulbs lasted on each of the twelve machines is given in the table. Lifetimes of light bulbs (hours) Infocus 611, 1046, 1030, 875, 771, 890, 885, 1164, 917,923, 1115,625 Proxima 848, 680, 986, 917, 924, 984, 1082, 831, 744, 910, 843, 1047 Assume that the two populations of lifetimes are normally distributed and that the population variances are equal. Can we conclude, at the level of significance, that there is a difference in the mean lifetime of the light bulbs in the two brands? Perform a two-tailed test. Then fill in the table below. Carry your intermediate computations to at least three decimal places and round your answers as specified in the table. 1. Null 2. Alternative 3. Test statistic 4. Value of test (round 3 dec) 5. P-value 6. Can we conclude that there is a difference in the mean lifetimes between two brands?