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What is meant by random sample?
Each item in a population has an equal chance of being chosen
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How do you take a random sample?
1) Number all the pieces of data. 2) Random number generator. 3) Select pieces of data which correspond to the random numbers.
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Comparing Box Plots
IQR, median, and skew (but only the inside of the box, not the whiskers)
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Quicker and cheaper
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Write a suitable question
1) Time frame. 2) Non-overlapping boxes. 3) "Other" box
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3D or distorted? Confusing gaps? Uneven scale on axis?
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Which distribution is it?
Uniform - Each outcome has an equal chance. Binomial - mutually exclusive events. 3) Normal - naturally occurring.
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Comparative pie charts
Always about area of pie charts
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Scatter graphs +line of best fit
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Relationship between two variable on scatter graphs
1) Positive/negative 2) As one gets bigger/smaller the other gets bigger/smaller
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Why use a control group?
Compare the impact of change on a group that has had no change.
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Why pilot survey?
1) Check q's are understood. 2)Relevant answers. 3) Check response rates. 4) Can change q's. 5)How long it will take.
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Suitable sample?
Equal chance of being chosen? Biased in any way?
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What sample frame could be used?
Needs to be a specific population, ie list of everyone in payroll or everyone on electrical register.
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Quick, cheap, less accurate, may suffer from bias.
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Describe trends.
Focus on trends, not numbers. So: Population increases in size (not: goes from 20 to 40)
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Why take/what is a stratified sample?
Proportionally represents the population.
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## Other cards in this set

### Card 2

#### Front

How do you take a random sample?

#### Back

1) Number all the pieces of data. 2) Random number generator. 3) Select pieces of data which correspond to the random numbers.

### Card 3

#### Front

Comparing Box Plots

### Card 5

#### Front

Write a suitable question