Statistics Flashcards

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1
Q

what are three reasons you would use the sample instead of the population data?

A

1. population data is not available
2. population data is available but is so large it would be v difficult to analyse
3. sample data is quicker

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2
Q

variance symbol

A

σ2 
sigma squared

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3
Q

discreet vs continuous variable

A

discreet is countable (amount in bank account), continuous is measureable (time)

e.g. age is a continuous variable because you are 25, and 40 days, and 4 hours, a 3 minutes, and 2 seconds, a 23 picoseconds. You can make age discreet by limiting it to your age in years.

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4
Q

variance definition

A

average of the squared difference from the mean

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5
Q

vector (in R)

A

way to store data

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6
Q

parameter

A

a characteristic of a population

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7
Q

statistic

A

a characteristic of a sample 

vs a parameter which is a character of a population

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8
Q

4 levels of measurement

A

- nominal : categories, not ordered e.g. race 

- ordinal : ordered but differences are meaningless e.g. rank in a race, 1st, 2nd, 3rd

- interval : ordered and differences are meaningful but there is no natural zero e.g. temperature 

- ratio : interval measurements where there is a natural zero e.g. money

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9
Q

why do you square every difference from the mean when calculating variance?

A

to make them all positive numbers 
e.g. if you had a 5 and a -5 they would cancel eachother out, so the variance would 0.

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