Mr. Rogers - AP Statistics Objectives
 Unit Plan Practice Test Study Guide

AP Statistics  Practice Test Sampling Distributions Confidence Intervals Chapt 9 & 10

1 ) According to the central limit theorem, the sampling distribution: 1) gets narrower or has less variability and 2) more closely resembles a normal distribution as sample size increases..

2 ) The average height all monkeys is 48 with a standard deviation of 2 inches. What is the standard deviation of monkey heights for the sampling distribution of size ten? SE = 2 / (10)0.5

3 ) What effect does population size have on the mean and standard deviation of a sampling distribution? no effect on the mean or std dev

4 ) Generally a statistic is used for estimating a corresponding parameter.

5 ) Indicate which of the following can fit the binomial setting. Y=yes, N=no

 yes       If 90 % of consumers buy corn flakes then what is the probability of randomly choosing 100 who don't buy corn flakes.
 no , p is not constant  If a barrel of 10 monkeys contains 2 albino monkeys what is the probability of getting both albinos in a given draw assuming no monkeys are replaced after being drawn.
no, p is not constant   If 45% of all students wore Bob's Jumpy Shoes in 1978 what is the probability of finding a random sample of 20 students that wear Bob's Jumpy Shoes the year 2057?

6 ) If the width of a confidence interval triples, what also had to happen to the margin of error? 3x

7 ) If the sample size is increased by a factor of 2, what is the effect on the margin of error?

new ME change = (1 / (2)0.5)*(old ME)

=  0.707(old ME)

8 ) If the confidence level is changed from 80% to 95% what is the effect on the margin of error?

% change = [(1.96-1.28) / 1.28]*100%

= 53%

9 ) Which type(s) of error(s) will the margin of error account for? Random sampling error or variability

10 ) What is the z* for a confidence level of 85%? 1.44

11 ) Which types of studies can make use of confidence intervals? SRS

12 What is the minimum sample size for determining the mean length of widgets in a manufacturing industry to a margin of error = plus or minus .2 given a 90% confidence interval and a standard deviation = 3.

ME = Z* ( σp/ n0.05)

n  (ME) = Z* ( σp)

n0.05 = (Z* σp) / (ME)

n = [(Z* σp) / (ME)]2

n = [1.64(3) / (0.2)]2

n = 605.1  rounding up, use 606

13 ) Which is more accurate, a margin of error with a confidence level of  65% or a margin of error with a confidence interval  of 90%? Can't tell.

14 ) For an 80 % confidence interval, we are confident that _______________ .
80 % of confidence intervals constructed around a sample statistic will contain the population parameter.