1.04 Quiz: Important Concepts From This Unit

Jeff is a snake charmer who can charm snakes with .78 probability of success. In a typical snake-charming season, Jeff attempts to charm 400 snakes. Using the exact binomial calculation, find the probability that he'll charm fewer than 300 snakes.

.067

If you flip three coins simultaneously, what's the probability you'll get three heads for the first time on the fifth toss?

.0733

In a survey, 1,000 mothers and fathers are asked about the importance of sports for boys and girls. Of the parents interviewed, 75% said genders are equal and should have equal opportunities to participate in sports. Assuming that .75 is correct for the population, what are the mean, standard deviation, and shape of the distribution of the sample proportion p-hat for n = 100?

.75, .0433, approximately normal

A commercial crabber catches more than 1,000 crabs and measures the shells, and finds the mean length is 6.8 inches with a standard deviation of 3.2 inches. Assuming these measures are true for the population, if the crabber takes many random samples of size 50, what proportion of the sample means would we expect to be greater than 6 inches?

.9615

Which answer shows 1. The mean of the distribution of x-bar 2. The standard deviation of the distribution of x-bar 3. The mean of the distribution of p-hat 4. The standard deviation of the distribution of p-hat

1. µ subx-bar = µ 2. σ subx-bar = σ / √n 3. µ subp-hat = p 4. σ subp-hat = √p(1-p) / n

Suppose you flip a coin n times, and the probability of getting heads 15 times is .0148. What's n?

20

Suppose voters from a simple random sample of 500 (N > 1,000,000) are interviewed and asked which presidential candidate they're going to vote for. Of these, 35% say they'll vote for the Statistics Party. You want to know the probability, assuming this proportion is correct for the population, that more than 40% of a random sample of 500 people will vote for the Statistics Party. Which of these shows the three ways you could find your answer?

Proportion, using normal approximation: normalcdf (.40, E99,.35,.0213) Exact binomial count: 1 - binomcdf (500,.35, 200) Binomial count, using normal approximation: normalcdf(200, E99, 175 ,10.66)

A twenty-sided number cube, with the faces numbered 1 to 20, is rolled 100 times. What's the exact probability of getting more than 15 elevens but at most 30 elevens?

binomcdfleft (100, 1/ 20, 30) - binomcdf(100 , 1/20, 15)

Suppose you're playing a game where you roll two number cubes. If you get doubles on or before the fourth roll you win the game. What's the probability of winning?

geometcdf(1/6, 4)

John is an expert horseshoe thrower who only misses 15% of the time. Choose the expression that correctly represents the probability John will miss fewer than 50 times if he throws 400 horseshoes.

normalcdf(-E99, 50, 60, 7.14)