Statistics Practice 1: Grouped Data and Mean

Concept Check

Question 1mcq

In the grouped table

0-10:4, 10-20:7, 20-30:9

, what is the class width?

A.

4

B.

20

C.

30

D.

10

Question 2mcq

For the class interval

40-50

, which pair represents its lower and upper limits?

A.

45

and

50

B.

40

and

45

C.

40

and

50

D.

39.5

and

49.5

Question 3mcq

What is the class mark of the interval

20-30

?

A.

30

B.

25

C.

10

D.

20

Question 4mcq

The intervals are

10-20,20-30,30-40

. Which list gives their class marks?

A.

15,25,35

B.

10,20,30

C.

20,30,40

D.

5,10,15

Question 5mcq

For grouped data with class marks

5,15,25

and frequencies

2,3,5

, what is the mean?

A.

15

B.

16

C.

20

D.

18

Apply and Analyse

Question 6mcq

A table has

\sum f_i x_i=1260

and

\sum f_i=42

. What is the mean by the direct method?

A.

1260

B.

35

C.

30

D.

42

Question 7mcq

Using assumed mean method, if

a=40

,

\sum f_i d_i=120

and

\sum f_i=30

, what is the mean?

A.

120

B.

44

C.

36

D.

40

Question 8mcq

A student using assumed mean takes

a=50

and gets

\sum f_i d_i=-80

,

\sum f_i=20

. What should the mean be?

A.

46

B.

54

C.

50

D.

-4

Question 9mcq

For class marks close to

100

and large frequencies, which mean method is usually most efficient?

A.Counting raw observations one by one

B.Mode formula

C.Median formula

D.Assumed mean method

Question 10mcq

A student uses the upper limit

30

as the class mark of

20-30

. What is the mistake?

A.The class width is zero.

B.The lower limit should be ignored.

C.The class mark should be the midpoint,

25

.

D.The frequency should be

30

.