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NZAMT NZQA NZ Grapher NZ Maths Census at School Study It

3.10 Inference HOME | Achievement Objectives | Overview | Statistical Cycle | Introduction & Research Question | Discussing Samples | Sample Variability | Sampling Methods | Informal Confidence Interval | Bootstrapping Confidence Interval | Comparing two populations | Using iNZight | Writing a report | Assessment Practice

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

Starter 5

Class notes,Class notes
Class site

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…


About Box plots (Murdoch university)

Max =

Upper Quartile =

Median =

Lower Quartile =

Minimum =

"An investigator only gets to see one frame of the movie"


What happens if we change the sample size?

A Sample size n = 15

A Sample size n = 60

Links to Census at school Animations page

Sample size n = 10 animation


Sample size n = 100 animation


Sample size n = 1000 animation





More animations like this at Census at school Animations page



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