1, In a survey, 31 people were asked how much they spent on their child's last birthday gift. The results were roughly shaped as a normal curve with a mean of $33 and standard deviation of $7. Construct a confidence interval at a 98% confidence level.

Give your answers to one decimal place.

(Note this is NOT in interval form, so check your answer carefully)

2, Karen wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 61 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 11.5 and a standard deviation of 2.1. What is the 98% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Enter your answers accurate to 4 decimal places.

[,] (Report and round to 4 decimal places)

3, You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximate=39.3 You would like to be 99% confident that your estimate is within 0.5 of the true population mean. How large of a sample size is required?

As in the reading, in your calculations:

--Use z = 1.645 for a 90% confidence interval

--Use z = 2 for a 95% confidence interval

--Use z = 2.576 for a 99% confidence interval.

n=

4, We wish to estimate what percent of adult residents in a certain county are parents. Out of 300 adult residents sampled, 45 had kids. Based on this, construct a 95% confidence interval for the proportionppof adult residents who are parents in this county.

Give your answers as decimals, to 4 places.

Answer =

(Note this is NOT in interval form, so check your answer carefully)

5, Consider a simple poll that is measuring the proportion of citizens that hold a particular political belief. What is a conservative, "worst case scenario" sample size if you want the margin of error to be 2.1%?

Sample Size =

6, A medium-sized store in Phoenix is run by Todd, who is studying the number of customers that visit the store each day. Todd takes a random sample of 45 daily customer totals. The sample has a mean of 369 people. Assume the population standard deviation is 43 people. Based on this sample, construct a 95% confidence interval for the true population mean of the daily customer total.

Do not use StatCrunch. Show all formulas used, work and steps. Be sure to define your variables.

As in the reading, in your calculations:

--Usez= 1.645 for a 90% confidence interval

--Usez= 1.96 for a 95% confidence interval

--Usez= 2.576 for a 99% confidence interval

Give your interval values rounded to one decimal place.Then interpret your answer in a complete sentence within the context of the problem.