1.Recently a survey was done to determine the mean electric bill in the Northfield area. Residents were contacted and the mean bill was equal to $120 with a standard deviation of $50.

1. If a random sample of 30 homes is selected what is the probability that electric bills will exceed $140?

1. If a random sample of 40 homes is selected what is the probability that electric bills will lie between $110 and $140?

1. In that same sample of 40 homes 67% of all students will have electric bills greater than what amount?

2.A random sample of 65 fields of wheat has a mean yield of 26.8 bushels and standard deviation of 8.0 bushels per acre.

1. What is the 90% confidence interval to estimate the population mean yield of wheat?

1. What is the 99% confidence interval to estimate the population mean yield of wheat?

3.In a recent study by the USDA 500 men were asked if they are comfortable with food irradiation, 340 said they are comfortable and do not mind if food has been irradiated. The other 160 said they do not favor irradiating food for any reason.

1. What is the 95% confidence interval for the true population proportion of men who are comfortable with food irradiation?

1. What is the 95% confidence interval for the population proportion of men whom do not favor irradiating food for any reason?

4.A recent article in the Northfield News reported that auxiliary units (rec. center, student center) will be facing significant increases in their daily costs of operations. How many days would need to be sampled if we are to be 95% confident that an estimate of mean daily operating costs will be within $100. The standard deviation based on previous studies is $400 per day

5.You are a travel agent and wish to estimate with 98% confidence, the proportion of travelers who use the internet to make reservations for hotel lodgings.Your estimate must be accurate within 4% of the population proportion.

1. If no preliminary estimate is available, find the minimum sample size

1. A coworker finds a report that indicates 20% of travelers use the internet to make reservations for hotel lodgings. Would the minimum sample size change?If yes to what number of individuals.

6.The average heartbeat pulse rate among Americans between the ages of 20 and 25 is 89 beats per minute with a standard deviation of 5 beats per minute.A researcher in Physical Education at Norwich samples 42 students who regularly exercises and discovers the mean heartbeat pulse rate is 87 beats per minute.At the 0.10 level of significance can it be concluded that students who exercise have heartbeat pulse rates less than the average for Americans between the ages of 20 and 25.

a.State the null and alternative hypotheses.What is the decision rule?

b.What is your decision concerning the null hypothesis? Compute and interpret the p-value

Interpret your decision.

7.Hawaiian Tropic recently ended a marketing and promotion campaign for their new line of sun block products containing their patented sunsure technologies.Previous to the campaign 50% of those who use Hawaiian Tropic products used older sun block products. The company surveyed bathers on beaches from Maine to California and found that of a sample of 3,850 users of Hawaiian Tropic products, 2002 were using the new technology sun block products. At the 0.05 level of significance can we conclude that a greater percentage of individuals are using the newer sun block product?

a.State the null and alternative hypotheses.What is the decision rule?

b.What is your decision concerning the null hypothesis? Compute and interpret the p-value

Interpret your decision.

8.A recent national study concluded that the average mean amount of sodium in a typical serving of cereal is equal to 230 milligrams.You find that in a random sample of 52 cereal servings the sodium content is equal 235 milligrams of sodium with a standard deviation of 10 milligrams. At the 0.05 level of significance can we conclude that the sodium level in your sample is different than the recent national survey results?

a.State the null and alternative hypotheses.What is the decision rule?

b.What is your decision concerning the null hypothesis? Estimate the p-value

Interpret your decision.

Based upon your data develop a 95% confidence interval for the national average mean amount of sodium in a typical serving of cereal.What do you conclude? Compare with the hypothesis test you did above