Ch.10 Lesson 1 PERFORM

The Bureau of Labor Statistics announces that last month it interviewed all members of the labor force in a sample of 60,000 households: 4.9% of the people interviewed were unemployed. The underlined number is...

• a sampling distribution

• parameter

• statistic

A study of voting chose 663 registered voters at random shortly after an election. Of these, 72% said they had voted in the election. Election records show that only 56% of registered voters voted in the election. The underlined number is a...

• a sampling distribution

• parameter

• statistic

Law of Large Numbers (LLN)

Annual returns on the more than 5000 common stocks available to investors vary a lot. In a recent year, the mean return was 8.3% and the standard deviation was 28.5%. The Law of Large Numbers says that...

• you can get an average return higher than the mean 8.3% by investing in a large number of stocks.

• as you invest in more and more stocks chosen at random, your average return on these stocks gets even closer to 8.3%.

• if you invest in a large number of stocks chosen at random, your average return will have approximately a Normal distribution.

Central Limit Theorem (CLT)

Scores on the mathematics part of the SAT exam in a recent year were roughly Normal with mean 515 and standard deviation 114. You choose an SRS of 100 students and average their SAT math scores. If you do this many times, the mean of the average scores you get will be close to...

• 515

• 500/100 = 5.15

Central Limit Theorem (CLT)

Scores on the mathematics part of the SAT exam in a recent year were roughly Normal with mean 515 and standard deviation 114. You choose an SRS of 100 students and average their SAT math scores. If you do this many times, the standard deviation of the average scores you get will be close to...

• 114

• 114/100 = 1.14

Central Limit Theorem (CLT)

The number of hours a light bulb burns before failing varies from bulb to bulb. The distribution of burnout times is strongly skewed to the right. The central limit theorem says that...

• as we look at more and more bulbs, their average burnout time gets even closer to the mean μ for all bulbs of this type

• the average burnout time of a large number of bulbs has a distribution of the same shape (strongly skewed) as the distribution for individual bulbs

• the average burnout time of a large number of bulbs has a distribution that is close to Normal

The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean 266 days and standard deviation 16 days. The probability that the average pregnancy length for 6 randomly chosen women exceeds 270 days is about...

• 0.40

• 0.27

• 0.07