Descriptive Statistics Flashcards

1
Q

What are descriptive statistics?

A

they described the data shown as a number which summarises the observed data
only tells us about sample

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2
Q

What are the 2 types of descriptive statistics

A

measure of central tendency
measures of dispersion (or spread)

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3
Q

What are the measures of central tendency?

A

mean, median, mode

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4
Q

what is a strength of the mode?

A

easy to calculate and not distorted by extreme values

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5
Q

what is a weakness of the mode?

A

focuses only on one value

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6
Q

what is a strength of the median?

A

less affected by outliers

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7
Q

what is a weakness of the median?

A

only uses 1-2 data points so doesn’t take into account all the data

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8
Q

what is a strength of the mean?

A

good representation of the data set due to taking all values into account

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9
Q

what is a weakness of the mean?

A

affected by extreme values, not useful for nominal data

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10
Q

What data level is linked to the mode?

A

nominal data

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11
Q

what data level is linked to the median?

A

ordinal

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12
Q

what data level is linked to the mean?

A

interval

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13
Q

what are the measures of dispersion?

A

range, interquartile range, variance, standard deviation

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14
Q

what is the range?

A

differences between the highest and lowest variable

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15
Q

what is the IQR?

A

you remove the upper an lower 25% of data, then complete the range in the middle 50% of scores

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16
Q

What is variance?

A

measure of how much values in a data set differ from the mean

17
Q

How do you calculate variance?

A

find mean of data
find difference between each value and the mean
square each difference
add up squared differences
divide sum of squared differences by no. of data points

18
Q

what is S.D?

A

square root of variance

19
Q

Strengths and Weaknesses of range

A

+ easy to calculate
- effected by extreme values
- doesn’t take into account all data values

20
Q

strengths and weaknesses of IQR

A

+ less effected by extreme values
+ good for ordinal data
- doesn’t use all the data values

21
Q

strengths and weaknesses of S.D

A

+ scale invariance
+ uses all the scores
- time consuming to conduct

22
Q

strengths and weaknesses of variance

A

+ treats all deviations the same
- sample size

23
Q

normal distribution

A

symmetric, few extreme scores on each end, bell shaped curve
mean, median and mode close together

24
Q

Skewed distributions

A

majority of scores on one end
extreme scores affect mean

25
Positively skewed distribution
data extends to right side most data clustered on left mode, median then mean extends off
26
Negatively skewed distribution
data extends to the left side of the most data clustered on the right mean, median, then mode (right side)
27
What descriptive statistic would you use for interval/ratio data with a skewed distribution?
median range
28
what descriptive statistic would you use for interval/ratio data with a normal distribution?
mean standard deviation