Practice Quiz: Chapter 3

1(points: 2½)  SAT verbal scores are normally distributed, with a mean of 500 and standard deviation of 100. You randomly select a test taker. What’s the probability that s/he scored between 500 and 700?

2(points: 2½) Mensa, the largest high-IQ society, accepts SAT scores as indicating intelligence. Assume that the mean combined SAT score is 1000, with standard deviation 200. Jacinto scored a combined 1390.

Maria took a traditional IQ test and scored 129. On that test, the mean is 100 and the standard deviation is 15.

From the test scores, who is more intelligent? Explain.

3(points: 1) In a particular data set, the mean is 8700 and the median is 5000. What if anything can you say about the shape of the distribution?

Class Bounds	Frequencies, f
470.0–480.0	15
480.0–490.0	22
490.0–500.0	29
500.0–510.0	50
510.0–520.0	38

4(points: 5)  At right is a sample shown as a grouped frequency distribution. Compute the following quantities and label each with its name or its proper symbol: (a) sample size, (b) mean, (c) standard deviation, (d) variance. Round to two decimal places.

Use any valid method, but show your work. (Begin by filling in the third column including column heading.)

Here are the sale prices of 15 randomly selected houses in Joliet IL in December 2004, from Sullivan, Michael, Fundamentals of Statistics (Pearson Prentice Hall, 2008), page 171:

138,820   169,541   135,512   149,143   140,794   153,146   99,000   136,924
136,833   115,000   124,757   128,429   157,216   149,380   136,529

5(points: 4) Compute the five-number summary and make a box plot. (You might want to do that on your TI-83 and copy the plot to your paper.)