Confidence Flashcards

1
Q

What is significance?

A
  • Probability of H0 being true

- OR if H0 is true, how likely would the observed outcome be?

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2
Q

What is a type I error?

A

A ‘false positive’ - concluding there is a relationship/pattern/presence when there’s not

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3
Q

What is a type II error?

A

A ‘false negative’ - concluding there is no relationship when there is one

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4
Q

Which type of error is preferable in geography?

A

Type II

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5
Q

How do we minimise error?

A

Low significance thresholds

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6
Q

Describe the love canal error

A
  • Love Canal, NY state
  • Former landfill site - 22,000 tonnes of waste
  • Sold at auction with no mention of contamination
  • 1977 rain caused chemicals to come to surface
  • Birth defects, skin disorders, leukaemia
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7
Q

Describe the Andrew Wakefield error

A
  • Falsely linked MMR vaccine to autism in children aged 3-10 years
  • Parents didn’t vaccinate their children
  • Immunisation dropped from 92% to 73% in the UK
  • Data had been misinterpreted
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8
Q

How to we avoid error?

A
  • Challenge statistical tests for robustness

- Think about how big a sample you need before collecting data

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9
Q

Why do we need a large sample?

A
  • Increasing sample size increases the statistical power of the test
  • Large samples allow small changes to be detected
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10
Q

What is standard error of the mean?

A
  • Standard deviation of the mean of the means of a number of samples from the same population
  • Can be calculated from a single set of measurements
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11
Q

What is the central limit theorem?

A

Given a sufficiently large sample size from a population with a finite level of variance, the mean of all samples from the same population will be approximately equal to the mean of the population

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12
Q

How is standard error calculated?

A

Std. Error = (std.dev of population)/square root of n

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13
Q

For a large population the mean distribution is approximately….

A

Normal, even if the population distribution is not

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14
Q

What is standard deviation?

A

How individuals differ from the sample mean

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15
Q

How do we estimate standard error if we don’t know the population mean?

A

Estimated std.e = sample s/√(n-1)

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16
Q

What is the inference of standard error?

A

For a given population mean, it tells us how likely a particular sample mean is

17
Q

The larger the sample the…

A

Smaller the standard error and standard deviation

18
Q

Why is standard error important?

A
  • Allows us to calculate a confidence interval
19
Q

What is a confidence interval?

A
  • A range of values in which the true population mean lies