BIOL132 - L4

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  • Created by: Katherine
  • Created on: 07-06-16 19:46
Sampling distribution
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What is the sample mean?
It is an estimate of the true mean (u) . Random unbiased sample
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Is the true mean constant?
Yes
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What is sampling distribution like?
Between repeated experiments, the mean wobbles.
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What is the central limit theorem?
Sampling distribution for arithmetric mean is normal. Given enough prepeat calculations of mean. Irrrespective of underlying data distribution.
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What does the width of sampling distribution show?
It is essentially standard deviation of a normal distribution. Applied to sampling distribution - standard error.
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What is the standard error for a mean.
Width of the sampling distribution for a statistic.
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What is standard error for sample mean?
SE = standard deviation of the data/square root of n.
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What does standard error do?
It tells us how much wobble to expect under repeated experiments. It is a measure of the precision of an estimate.
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What can we calculated SE on?
Only one experiment - the formula depends on population standard deviation and sample size.
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What is the confidence interval?
The confidence interval is that for 95% of samples, the mean will be within =2SE of u.
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What is the confidence interval concept?
We know standard error and mean, but not u! Centre the sampling distributino over X instead. For 95% of samples, u will be within = 2se.
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Confidence intervals:
CI = mean +- 1.96 x SE
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Confidence interval summary?
For 95% of samples, u will be within =2SE of the mean.
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Confidence interval summary continued:
Measure of distance our estimated mean lies from the true mean. Gives us a measure of confidence in the estimate. Larger sample - > narrower CL. Likely to be more accurate. It is usually written as (lower cl, upper CL)
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What are sample based statistics?
Random - Sampling distribution, sampling distribution is Normal with mean u.
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What does standard error do?
It measures the width of the sampling distribution
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What do confidence intervals do?
They measure how likely an estimate mean is to be close to the true value.
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Card 2

Front

What is the sample mean?

Back

It is an estimate of the true mean (u) . Random unbiased sample

Card 3

Front

Is the true mean constant?

Back

Preview of the front of card 3

Card 4

Front

What is sampling distribution like?

Back

Preview of the front of card 4

Card 5

Front

What is the central limit theorem?

Back

Preview of the front of card 5
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