11. In a sample of 20 men, the mean height was 178 cm. In a sample of 30 women,

Question

11. In a sample of 20 men, the mean height was 178 cm. In a sample of 30 women, the mean height was 164 cm. What was the mean height for both groups put together? 12. In a study of visual perception, five people were asked to estimate the length of a line by eye and then to mea- sure it with a ruler. The results, in cm, were: By eye: 8.0, 9.0, 7.5, 9.5, 8.5 With a ruler: 8.1, 8.2, 8.1, 8.1, 8.3 a. Compute the mean measurement for each method. b. Compute the median measurement for each method. ments for each method. largest? Why should one expect this method to C. Compute the standard deviation of the measure d. For which method is the standard deviation the have the largest standard deviation?

Explanation / Answer

Ans 11

Average = (20*178+30*164)/(20+30) = 169.6 cm

Ans 12

a)

Mean By eye: 8.5

Mean By ruler: 8.16

b)

Median By eye: 8.5

Median By ruler = 8.1

c)

standard deviation by eye: 0.79

standard deviation by ruler: 0.09

d)

By eye the standard deviation is the largest and this is so because this method is perception based and highly susceptible to human error

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