# Stats Library

## Statistics Assignment Library

1. ##### A survey of 77 commercial airline flights of under 2 hours resulted in a sample average late time for a flight of 2.48 minutes.
A survey of 77 commercial airline flights of under 2 hours resulted in a sample average late time for a flight of 2.48 minutes. The population standard deviation was 12 minutes. Construct a 95% confidence interval for the average time...
2. ##### An electronic chess game has a useful life that is exponential with a mean of 30 months
An electronic chess game has a useful life that is exponential with a mean of 30 months. Determine each of the following: a. The probability that any given unit will operate for at least (1) 39 months, (2) 48 months,...
3. ##### The measured radius of a circle, R, has pdf
The measured radius of a circle, R, has pdf \begin{aligned} f(r) &= 6r(1-r),\; 0 < r < 1 \end{aligned} (a) Find the distribution of the circumference. (b) Find the distribution of the area of the circle. Solution (a)...
4. ##### The first assignment in a statistical computing class involves running a short program. If past experience indicates
The first assignment in a statistical computing class involves running a short program. If past experience indicates that 40% of all students will make no programming errors, compute the (approximate) probability that in a class of 50 students a. At...
5. ##### Among all the computer chips produced by a certain factory, 6 percent are defective.
Among all the computer chips produced by a certain factory, 6 percent are defective. A sample of 400 chips is selected for inspection. a) What is the probability that this sample contains between 20 and 25 defective chips (including 20...
6. ##### Resistors labeled 100 Omega have true resistances that are between 80 Omega and 120 Omega.
Resistors labeled 100 $\Omega$ have true resistances that are between 80 $\Omega$ and 120 $\Omega$. Let X be the mass of a randomly chosen resistor. The probability density function of X is given by  \begin{aligned} f(x)=\left\{ \begin{array}{ll} \frac{x-80}{800} &...
7. ##### A certain college gives aptitude tests in the sciences and the humanities to all entering freshmen.
A certain college gives aptitude tests in the sciences and the humanities to all entering freshmen. If X and Y are, respectively, the proportions of correct answers that a student gets on the tests in the two subjects, the joint...
8. ##### The average cost of an IRS Form 1040 tax filing at Thetis Tax Service is
The average cost of an IRS Form 1040 tax filing at Thetis Tax Service is \$157.00. Assuming a normal distribution, if 70 percent of the filings cost less than \$171.00, what is the standard deviation? Solution Let $X$ denote the...
9. ##### The distribution of the SAT scores in math for an incoming class of business students has a mean of 590 and Standard deviation
The distribution of the SAT scores in math for an incoming class of business students has a mean of 590 and Standard deviation of 22. Assume that the scores are normally distributed. a. Find the probability that an individual's SAT...
10. ##### The daily water consumption for an Ohio community is normally distributed with a mean consumption
The daily water consumption for an Ohio community is normally distributed with a mean consumption of 800,000 gallons and a standard deviation of 80,000 gallons. The community water system will experience a noticeable drop in water pressure when the daily...