Interpreting Estimates Intervals for Proportions Intervals for Known Sigma Intervals for Unknown Sigma Sample Size

Interpreting Estimates % of people agree with the bill with a margin of error of 5%. What is the interval estimate for the true proportion of supporters? Between 43-53%

Interpreting Estimates 200 A sample of 98 AHS students find that 62 of them are going out of town for Spring Break. What is the point estimate for the proportion of students leaving town?.63 or 63%

Interpreting Estimates 300 For the sample of ACT scores below, what is the point estimate for the mean?

Interpreting Estimates 400 S x = 3.93 For the sample of ACT scores below, what is the deviation?

Interpreting Estimates 500 The polls show Candidate A has approximately 48% of support, and Candidate B has 42% of the support. Both have a margin of error of 4%. Can you determine who will win. Why or why not? No, Candidate A can have between 44-52% of the vote, and Candidate B can have between 38-46% of the vote. Since the intervals overlap, no conclusions can be drawn.

Intervals for Proportions 100 At lunch, 38% of AHS students bring their own lunches. At a typical lunch of 220 students, how many will be bringing their lunches? 83.6 or 84

Intervals for Proportions 200 Which will give you a wider confidence interval: 90% confidence or 99% confidence? 99% confidence (in order to be more certain, the range of possibilities must increase)

Intervals for Proportions % of 1000 voters stated that they voted for the bill. Construct the 95% confidence interval (.45,.51)

Intervals for Proportions 400 A survey of 2450 golfers showed that 281 of them are left-handed. Construct a 98% confidence interval for the proportion of golfers who are left handed (.10,.13)

Intervals for Proportions 500 A newspaper selected a simple random sample of 1,600 subscribers. They asked whether the paper should increase its coverage of local news. Forty percent of the sample wanted more local news. Construct the 99% confidence interval. Can you conclude that at least 38% of readers would like more coverage of local news? (.37,.43); No b/c part of the interval is below 38%

Intervals for Known Sigma 100 What is the value of z c for 99% confidence? z c = 2.58

Intervals for Known Sigma 200 The average GPA of a sample of 50 AHS students is 3.4 with a known deviation of.15. Construct a 90% confidence interval for the GPA of all AHS students (3.37, 3.43)

Intervals for Known Sigma 300 Suppose we want to estimate the average weight of US adult males. We draw a random sample of 1,000 men and weigh them. We find that the average man in our sample weighs 180 pounds, and the standard deviation of the population is known to be is 30 pounds. What is the 95% confidence interval? (178.14, )

Intervals for Known Sigma 400 A sample of Alzheimer's patients are tested to assess the amount of time in stage IV sleep. The number of minutes spent is Stage IV sleep is recorded for 61 patients, producing a mean of 48 minutes and (known deviation is 14 minutes). Compute a 95 percent confidence interval for this data. Interpret. (44.49, 51.51)

Intervals for Known Sigma 500 A standardized test is used to assess students knowledge of world events A sample of 30 students are tested (mean=58, known deviation=17.5). Compute a 99 percent confidence interval How do these students compare to the national average of 65? (49.77, 66.23); It is reasonable since 65 is in the interval

Intervals for Unknown Sigma 100 For a sample of 15 students, what is the value of t c for 80% confidence? t c = 1.345

Intervals for Unknown Sigma 200 (24.9, 29.1) The average ACT of a sample of 10 AHS students is 27 with a deviation of 2. Construct a 99% confidence interval for the GPA of all AHS students

Intervals for Unknown Sigma 300 Your hot sauce company rates its sauce on a scale of spiciness of 1 to 20. A sample of 20 bottles of hot sauce is taste-tested, resulting in a mean of 12 and a deviation of 2.5. Find a 90% confidence interval for the spiciness of your hot sauce. (11.03, 12.97)

Intervals for Unknown Sigma 400 The CEO of your hot sauce company demands an average s spiciness of at least 13 (on a scale of 1-20). You randomly sampled 8 bottles of the new sauce and found an average spiciness of 13.5 with a deviation of Can you be 90% sure that the mean spiciness of the new sauce is above 13? (13.11, ); Yes both #’s are above 13

Intervals for Unknown Sigma 500 A sample of students were polled regarding the number of hours they spent studying for the last exam. Their data are below: Compute a 95 percent confidence interval. (8.55, 13.28)

Sample Size 100 A previous poll found that 38% favored the passing of a certain bill. What is the minimum sample size needed to conduct a new poll to be accurate within 2% at 99% confidence? 3921

Sample Size The average GPA of a sample of AHS students is 3.4 with a deviation of.15. How large a sample is needed to be accurate within.05 at 95% confidence?

Sample Size 300 How does sample size affect the width of the confidence interval? A larger sample size (which should yield more accurate results) will give a narrower interval

Sample Size 400 A researcher wishes to estimate the proportion of adults who have high blood pressure. How large of a sample is needed to be 98% confident that you are within 6%? 376

Sample Size 500 Prices for a 2005 Honda Civic range from $10748 to $ How many car prices should be included in my sample if I want to be within $100 of the actual average price at 90% confidence? Deviation = n = 188