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# Sample Variability

 Sample variability Overview of population concepts: mean & standard deviation, and distribution Video Chris Wilds overview of sample variation etc, time 0:00 to 7:23 Sample Variability - how each sample varies from other samples (but is similar) The effect of Sample size 'n' on sample variability, box plots and representation of the population. Use iNZight 'Sampling Variation' tool to present the concepts using the dolphin data set. In your report: 1) (MUST Do) You need to show an understanding that if they were to take another sample from the population this is likely to result in different displays and summary statistics. 2. (Should Do) Discuss the effect of differing sample size 3. (Could do) Discuss factors that influence / effect the width of the confidence interval continue with sampling methods Activity: take sample from a population (data cards) manipulate, make box plots, compare with rest of class, increase sample size Links to Census at school Animations page Sample size n = 10 animation Sample size n = 100 animation Sample size n = 1000 animation IAS 3.10 pg 10-14

Key Concepts
Taking a sample
Calculate Sample Statistics
Box plots
Sample Variability

A population has (usually) unknown
parameters: mean and median

Take a sample eg size n = 9

The sampling process should ensure the sample represents the population
A biased or poor sample will give poor population estimates

Calculate sample statistics

Make a box plot

Compare your box plot with other samples

What might the population median be?

We could use out sample median as an estimate, but we have a problem…

Max =

Upper Quartile =

Median =

Lower Quartile =

Minimum =