Question

Given the chart

Frequency Distribution of

IQ Scores of Low Lead Group

IQ Scores

Frequency

50

-

69

5

70

-

89

23

90

-

109

19

110

-

129

11

130

-

149

1

a.

Construct a Histogram

b.

Determine the Class Width

c.

Determine the Class Midpoint

d.

Find the class that contains the Median

e.

Use the Midpoint for each class to calculate the Mean

Answer 1

a)

class	frequency
50-69	5
70-89	23
90-109	19
110-129	11
130-149	1

b)

class width = 70-50 = 20

c)

class mid point = (lower limit+upper limit)/2

class	frequency	mid point
50-69	5	60
70-89	23	80
90-109	19	100
110-129	11	120
130-149	1	140

d)

class	frequency	mid point	cumulative frequenncy
50-69	5	60	5
70-89	23	80	28
90-109	19	100	47
110-129	11	120	58
130-149	1	140	59

N/2 = 59/2 = 29.5

so, median containing class is (90-109)

e)

class	frequency,f	mid point,X	cumulative frequenncy	X*F
50-69	5	60	5	300
70-89	23	80	28	1840
90-109	19	100	47	1900
110-129	11	120	58	1320
130-149	1	140	59	140
total	59			5500

mean=ΣXF/Σf = 5500/59=93.22