WORK SHT 1STATS
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Define STATISTICS
Differentiate between the branches of statistics
What do you understand about a quantitative variable vs. a qualitative variable?
Main point on cross section vs. time series data
Population-sample
Levels of measurement
List and describe different sampling techniques
Class Tally Frequency
A
1111 5
B
1111 7
11
O
AB
Percent
CLASS
TALLY
FREQUENCY
%
1111
1111
A
1111
5
20
1111
B
1111 11
7
28
O
1111 1111
9
36
AB
1111
4
16
Ʃf=25
100
WORK SHT 1STATS
Grouped data
These are used when range of data is large
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Class limits have the same value as the data, eg, 60 - 62
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Class Boundaries are not rounded numbers:
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Rule of thumb to find the lower and upper boundary:
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Lower limit - 0.5 = 60 - 0.5 = 59.5 = lower boundary
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Upper limit + 0.5 = 62 + 0.5 = 62.5 = upper boundary
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If you have been given, say, 7.8, then you need to subtract 0.05 for the lower boundary and
add 0.05 for the upper.
Class size/width= lower limit/boundary of a class – lower limit/boundary of preceding class.
Class mark or mid point= (upper limit + lower limit)/2
Midpoint tells an average of how many elements or members fall within class.
WORK SHT 1STATS
Some rules
1. There should be 5-20 classes.
2. The class width should be an odd number.
3. The classes must be mutually exclusive.
4. The classes must be continuous.
5. The classes must be exhaustive.
6. The classes must be equal in width (except in open-ended distributions).