Statatics for class 10

2. A Presentation
On Chapter –
14 (Statistics).

3. What is statistics?




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a branch of mathematics that provides techniques
to analyze whether or not your data is significant
(meaningful)
Statistical applications are based on probability
statements
Nothing is “proved” with statistics
Statistics are reported
Statistics report the probability that similar results
would occur if you repeated the experiment

4. Mean – arithmetic average = Σx/n
Median – the halfway point
Mode – the most common answer

5. Distribution Chart of Heights of 100 Control Plants
Looking at profile of data:
Distribution
• What is the frequency of distribution,
where are the data points?
Distribution Chart of Heights of 100 Control Plants
Class (height of plants-cm)
Number of plants in each class
0.0-0.9
3
1.0-1.9
10
2.0-2.9
21
3.0-3.9
30
4.0-4.9
20
5.0-5.9
14
6.0-6.9
2

6. Mode and Median
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Mode: most frequently seen value (if no
numbers repeat then the mode = 0)
Median: the middle number
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If you have an odd number of data then the
median is the value in the middle of the set
If you have an even number of data then the
median is the average between the two
middle values in the set.

7. 2-1 Frequency Distributions

Frequency Distribution
lists classes (or categories) of values, along
with frequencies (or counts) of the number
of values that fall into each class

8. Ogive
Upper Class Limit
(points are plotted at the upper right corner of each bar in
the histogram)

9. Definitions
Mean
(Arithmetic Mean)
AVERAGE
the number obtained by adding the values
and dividing the total by the number of
values

10. Statistical Computations (the Math)

If you are using a sample population
• Arithmetic Mean (average)
The sum of all the scores
divided by the total number of scores.

11. Definitions

Median
the middle value when the original
data values are arranged in order of
increasing (or decreasing) magnitude
~
not affected by an extreme value

12. Mean from a Frequency Table
use class midpoint of classes for
variable x
Σ (x • f)
x =
Σf
x = class midpoint
f = frequency
Σ f=n

13. Mean by Three Methods
• By Direct Method= fi.xi
•
•
fi
By Assumed Method=a+ fi.di
fi
By Step Deviation Method=a+ fi.ui X i
fi

14. For mula To Find
Mode
Mode=Highest Frequency=f1, class
Preceding to f1 = f0, class succeeding to
fi= f2, Lower Value in which f1 Lies, h=
class intervals.
 Mode= l+
f1 – f0 X h
2f1 – f0 – f2

15. Formula to find Median
 Median= n=total no. of observations;
divided by 2; becomes=n ,
2
 l =Lower Limit in which n lies, fi= class in
which n lies, c.f.= class preceding fi, h=
class intervals.
 Median=
n _ c.f.
l+ 2_________ X h
fi

16. Histogram-Frequency Distribution
Charts
This is called a “normal” curve or a bell curve
This is an “idealized” curve and is theoretical based on an infinite number
derived from a sample

17. 1) Statistics are useful for figuring out random
noise from real effects
2) Numbers are not absolute, and they can be
easily manipulated
3) Always scrutinize data closely, and draw
your own conclusions.
4) 85% of all statistics are made up on the
spot: the rest are all wrong