7.8 Review

$X$ ~

• A $U(\mathrm{0,4})$
• B $U(\text{10},2)$
• C $\text{Exp}(2)$
• D $N(\mathrm{2,1})$

The average wait time is:

• A 1 hour
• B 2 hour
• C 2.5 hour
• D 4 hour

Suppose that it is now past noon on a delivery day. The probability that a person must wait at least $1\frac{1}{2}$ more hours is:

• A $\frac{1}{4}$
• B $\frac{1}{2}$
• C $\frac{3}{4}$
• D $\frac{3}{8}$

Given: $X\text{~}\text{Exp}(\frac{1}{3})$ .

• a Find $P(x>1)$
• b Calculate the minimum value for the upper quartile.
• c Find $P(x=\frac{1}{3})$

• 40% of full-time students took 4 years to graduate
• 30% of full-time students took 5 years to graduate
• 20% of full-time students took 6 years to graduate
• 10% of full-time students took 7 years to graduate

The expected time for full-time students to graduate is:

• A 4 years
• B 4.5 years
• C 5 years
• D 5.5 years

Which of the following distributions is described by the following example?

Many people can run a short distance of under 2 miles, but as the distance increases, fewer people can run that far.

• A Binomial
• B Uniform
• C Exponential
• D Normal

The length of time to brush one’s teeth is generally thought to be exponentially distributed with a mean of $\frac{3}{4}$ minutes. Find the probability that a randomly selected person brushes his/her teeth less than $\frac{3}{4}$ minutes.

• A 0.5
• B $\frac{3}{4}$
• C 0.43
• D 0.63

Which distribution accurately describes the following situation?

The chance that a teenage boy regularly gives his mother a kiss goodnight (and he should!!) is about 20%. Fourteen teenage boys are randomly surveyed.

$X=$ the number of teenage boys that regularly give their mother a kiss goodnight

• A $B(\text{14},0\text{.}\text{20})$
• B $P(2\text{.}8)$
• C $N(2\text{.}\mathrm{8,2}\text{.}\text{24})$
• D $\text{Exp}(\frac{1}{0\text{.}\text{20}})$

Which distribution accurately describes the following situation?

A 2008 report on technology use states that approximately 20 percent of U.S. households have never sent an e-mail. (source: http://www.webguild.org/2008/05/20-percent-of-americans-have-never-used-email.php) Suppose that we select a random sample of fourteen U.S. households .

$X=$ the number of households in a 2008 sample of 14 households that have never sent an email

• A $B(\text{14},0\text{.}\text{20})$
• B $P(2\text{.}8)$
• C $N(2\text{.}\mathrm{8,2}\text{.}\text{24})$
• D $\text{Exp}(\frac{1}{0\text{.}\text{20}})$