Stat 200 Quiz and HW
i.mtti
quiz_2_summer_2015.docxQuiz 2
Each question is worth 1 point.
Don’t leave anything blank. I can always find a way to give you some credit if you’ve made an attempt. Be sure to post any questions you have after the answers open.
The work you turn in by 11:59 P.M. on June 28th must be your own.
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 P30, 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.
|
x |
P(x) |
|
0 |
0.539 |
|
1 |
0.351 |
|
2 |
0.095 |
|
3 |
0.014 |
|
4 |
0.001 |
|
5 |
0+ |
|
6 |
0+ |
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. Z0.02
b. Z0.01
c. Z0.10
