STAT 200 Quiz 2

1.    You draw two cards from a deck, what is the probability that:

a.    both of them are face cards (king, queen, or jack)?

b.    you draw two cards from a deck and both of them are hearts?

2.    Assume adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation of 15.

a.    Find the probability that a randomly selected adult has IQ < 115

b.    Find the probability that a randomly selected adult has IQ > 70

c.    Find P_30, which is the IQ separating the bottom 30% from the top 70%

3.    a. When would the mean grade in a class on a final exam be considered a statistic?

b. When would it be considered a parameter?

c.. Define bias in terms of expected value.

b.     Is it possible for a statistic to be unbiased yet very imprecise? Can it be accurate but biased?

4. a.  Why is a 99% confidence interval wider than a 95% confidence interval?

b. When you construct a 95% confidence interval, what are you 95% confident about?

5.    My parents lived in Florida and wanted to know the probability of winning the Florida

Fantasy 5 if they bought one ticket. They had to pick the five winning numbers from 1-

36. Each randomly selected number is different and order doesn’t matter. What is the

Probability of their winning?

6.     In a study of families with children with disabilities, group of 6 US households were

randomly selected. In the table below, the random variable x represents the number of

households among 6 that had a child with a disability living there.

a)    Is this a probability distribution?

b)    What is the mean?

c)    What is the standard deviation?

7.    Ten peas are generated from parents having the green/yellow pair of genes so there is a

75% probability that an individual pea will have a green pod. Find the probability that

among the 10 offspring peas, at least 9 have green pods. Is this unusual? Explain.

8.  Find the critical value:

a. Z_0.02

b. Z_0.01

c. Z_0.10