Question

Assume you are interested in determining if reaction times to identify letters presented on a computer screen differ according to time of day. You present the subjects in your study with a letter and measure how long it takes them to push a key on a keyboard in front of them (i.e. you measure their reaction time in milliseconds). Below is a set of reaction time data collected from 25 students in the late afternoon. 1) Construct a grouped frequency distribution table using the steps outlined in class. For this assignment use 6 interval classes to calculate your interval width. NOTE: this does not mean your final table has to have 6 categories (9 points). 2) In your table include columns expressing the relative frequencies of scores a proportion and percentages (9 points) 3) If you had to represent the frequency distribution graphically what type of graph would you choose? Why? (2 points) 30 23 58 28 41 35 67 48 27 42 53 46 55 41 33 18 53 25 30 38 32 48 36 31 39

Answer 1

(1) The values are ranged from 18 to 67. We define 6 classes, 10-20, 21-30, 31-40, 41-50, 51-60 & 61-70

The grouped frequency distribution is as below:

Class	Frequency
10-20	1
21-30	6
31-40	7
41-50	6
51-60	4
61-70	1

(2)

Relative frequency for the first class = 1/25 = 0.04 (proportion) and 4% (percentage).

The complete table is as below:

Class	Frequency	Relative Frequency (proportion)	Relative Frequency (%)
10-20	1	0.04	4%
21-30	6	0.24	24%
31-40	7	0.28	28%
41-50	6	0.24	24%
51-60	4	0.16	16%
61-70	1	0.04	4%

(3) For representing the above frequency distribution graphically, we choose histogram as the histogram provides frequency distributions for various class intervals lying in a particular range. The height of each bar in the histogram corresponds to the relative frequency of the amount of data in the class.