Question

hassan recorded the number of people in 60 passing cars

people 1 2 3 4 5 6
frqn 28 ? 3 7 1 1
find the missing frequency
median
modal
mean
will mark the brainest help me plz guys

Answer 1

Answer:

14.1 Introduction

In Class IX, you have studied the classification of given data into ungrouped as well as

grouped frequency distributions. You have also learnt to represent the data pictorially

in the form of various graphs such as bar graphs, histograms (including those of varying

widths) and frequency polygons. In fact, you went a step further by studying certain

numerical representatives of the ungrouped data, also called measures of central

tendency, namely, mean, median and mode. In this chapter, we shall extend the study

of these three measures, i.e., mean, median and mode from ungrouped data to that of

grouped data. We shall also discuss the concept of cumulative frequency, the

cumulative frequency distribution and how to draw cumulative frequency curves, called

ogives.

14.2 Mean of Grouped Data

The mean (or average) of observations, as we know, is the sum of the values of all the

observations divided by the total number of observations. From Class IX, recall that if

x1

, x2,. . ., xn

are observations with respective frequencies f

1, f2

, . . ., fn

, then this

means observation x1

occurs f

1

times, x2 occurs f

2

times, and so on.

Now, the sum of the values of all the observations = f1x1 + f2x2 + . . . + fnxn, and

the number of observations = f1

+ f2

+ . . . + f

n

.

So, the mean x of the data is given by

x = 11 2 2

1 2

n n

n

fx fx fx

ff f

 

 

L

L

Recall that we can write this in short form by using the Greek letter Σ (capital