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...