# BIOL132 - L4

?
• Created by: Katherine
• Created on: 07-06-16 19:46
Sampling distribution
f
1 of 18
What is the sample mean?
It is an estimate of the true mean (u) . Random unbiased sample
2 of 18
Is the true mean constant?
Yes
3 of 18
What is sampling distribution like?
Between repeated experiments, the mean wobbles.
4 of 18
What is the central limit theorem?
Sampling distribution for arithmetric mean is normal. Given enough prepeat calculations of mean. Irrrespective of underlying data distribution.
5 of 18
What does the width of sampling distribution show?
It is essentially standard deviation of a normal distribution. Applied to sampling distribution - standard error.
6 of 18
What is the standard error for a mean.
Width of the sampling distribution for a statistic.
7 of 18
What is standard error for sample mean?
SE = standard deviation of the data/square root of n.
8 of 18
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.
9 of 18
What can we calculated SE on?
Only one experiment - the formula depends on population standard deviation and sample size.
10 of 18
What is the confidence interval?
The confidence interval is that for 95% of samples, the mean will be within =2SE of u.
11 of 18
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.
12 of 18
Confidence intervals:
CI = mean +- 1.96 x SE
13 of 18
Confidence interval summary?
For 95% of samples, u will be within =2SE of the mean.
14 of 18
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)
15 of 18
What are sample based statistics?
Random - Sampling distribution, sampling distribution is Normal with mean u.
16 of 18
What does standard error do?
It measures the width of the sampling distribution
17 of 18
What do confidence intervals do?
They measure how likely an estimate mean is to be close to the true value.
18 of 18

## Other cards in this set

### 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 ### Card 4

#### Front

What is sampling distribution like?

#### Back ### Card 5

#### Front

What is the central limit theorem?

#### Back 