MATH200 — Practice Quiz: Chapter 7 — 20 min

# Practice Quiz: Chapter 7

Work this like a regular quiz, using only your crib sheet. Give yourself a maximum of 20 minutes, then turn to the solutions and see how you did.

Be sure to sketch and label your curve on appropriate problems. Round probabilities to four decimal places.

Remember, you must show your work for full credit on any problems involving computation.

1(points: 3½) Suppose that the new Ford Behemoth SUV gets a mean of 6.20 miles to the gallon, normally distributed with standard deviation 0.90 mpg. Jane, who has taken a statistics class, found that 85% of Ford Behemoths get better gas mileage than hers does. What is her car’s gas mileage, to two decimal places?

2(points: 1)  What is the percentile rank of Jane’s car?

3(points: 3½) The times to assemble a particular product part are normally distributed with a mean of 47.5 minutes and a standard deviation of 8.5 minutes. What percent of assembly workers require more than 60 minutes?

4(points: 1½) The standard normal curve is plotted in terms of _____ (write in “z” or “x”). It has a mean of _____ and a standard deviation of ___.

5(points: 3) The lifetimes of Everlast AA batteries are normally distributed. Between x=28.2 and x=34.1 hours, the area under the curve is 0.0742. Give two interpretations of this fact, in English.

6(points: 2½)  Fourteen rats were sent into space, and on their return to Earth their red-blood-cell masses were measured. Here are the data, in milliliters:

8.59   6.87   7.00   6.39   7.43   9.79   9.30   8.64   7.89   8.80   7.54   7.21   6.85   8.03

Are those figures normally distributed? Support your answer, but you need not draw a graph.

Solutions to this practice quiz are available at http://www.tc3.edu/instruct/sbrown/stat/