Worksheet 3 and 4 Practice Quiz

In a large company, a (random) poll of 622 employees was made and found that 512 never used tobacco products.

Construct a 90% confidence interval for the population proportion of the employees that reported they never used tobacco products. (hint: you must find the Critical Value & Margin of Error first)

Confidence interval ______________ < p < ______________

• .7978<p<.8482

• .8132<p<.8482

• .7978<p<.8132

• .8132<p<.8596

On worksheet #3 question #2 stated: In problem #1 above here, if you stay with the same values of p and q in this poll at the 90% Confidence Level and wish to have the Margin of Error (E) drop to 1.9% or .019. Then the sample size needs to increase to how many from the 622? What was your answer?

• 1,092

• 622

• 748

• 986

Many individuals think the results on a certain test will be normally distributed. Below are the results on this test from an average year:

24 24 25 27 28 29 31 31 33 35

35 35 35 37 38 40 44 46 50 50

Using the statistic modes on your calculator and table A – 3 for t-Values find the Margin of Error knowing it is at 90% confidence interval level and two tailed for this t-distribution :

• 3.209

• 1.645

• 1.729

• 8.001

On Worksheet #4 Quesion B stated: Construct a 90% confidence interval for the average score on this exam if it is given many

times over the next five years.

___________ < m < ____________. What was your answer?

• 31.14<u<37.56

• 32.26<u<37.56

• 31.14<u<32.26

• 32.26<u<39.42

Many instructors assume their students’ results will be (or should be) normally distributed. A certain instructor who believed this gave a standardized statistics exam every year. Here were his results for an average year:

54 47 58 55 67 82 83 84 72 63 52

92 75 71 68 74 71 73 55 45 50 60

Using the statistic modes on your calculator and table A – 3 for t-Values find the following knowing it is at 90% confidence interval level and two tailed for this t-distribution construct a 90% confidence interval for the average score on this exam.

• 61.16<u<70.74

• 61.16<u<72.96

• 62.48<u<70.74

• 62.48<u<72.96

In a small town with 4,000 residents, a (random) poll of 356 residents was made and found that 265 were over the age of 35. If they wanted the margin of error to be 3.5% then the sample size would need to be how many at the 95% Confidence Level?

• 597 residents

• 265 residents

• 492 residents

• 326 residents

What is the t value associated with 90% confidence and a sample size of 15?

• 1.341
• 1.345
• 1.761
• 1.753

What is the degrees of freedom equal to?

• n
• n+1
• 1-n
• n-1

The 90% interval for a statistics test was given by 72 +- 7. What is the lower bound for the interval?

• 7
• 72
• 65
• 79

Tags

CCSS.HSS.IC.B.4

Why do we use a t-distribution instead of a z-distribution for means?

• Because the population standard deviation is unknown.

• It allows us to decrease the margin of error without increasing our confidence level.

• It allows us to use the population standard deviation.

• None of these.

Tags

CCSS.HSS.ID.A.4