The frequency distribution below shows the distribution for IQ scores for a rand

Question

The frequency distribution below shows the distribution for IQ scores for a random sample of 1000 adults. (Show all work. Just the answer, without supporting work, will receive no credit.)

a) Complete the frequency table with frequency and relative frequency. Express the relative frequency to three decimal places.

(b) What percentage of the adults in this sample has an IQ score of at least 110?

(c) Does this distribution have positive skew or negative skew? Why or why not?

IQ SCORE FREQUENCY RELATIVE FREQUENCY 50-69 24 70-89 90-109 453 110-129 0.25 130-149 25 TOTAL 100

Explanation / Answer

a) frequency for 110-129 = 1000 * 0.25 = 250

frequecy for 70-89 = 1000 - (24 + 453 + 250 + 25) = 248

IQ scores                       Frequency                          Relative frequency

50-69                                 24                                         24/1000 = 0.024

70-89                                 248                                       248/1000 = 0.248

90-109                               453                                       453/1000 = 0.453

110-129                             250                                       250/1000 = 0.25

130-149                             25                                         25/1000 = 0.025

b) P(X > 110) = P(110-129) + P(130-149) = 0.25 + 0.025 = 0.275

c) This is right skewed distribution. Because the right tail is larger than left tail.

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