USE STATISTICAL METHODS TO MAKE AN INFERENCE

Achievement Standard 91264 – 4 credits, internal

Sir Richie McCaw?•Sir Richie McCaw? Read read read…

Sir Richie McCaw?

What was the survey question in each article?

How well do the views expressed reflect the views of all NZers?

Why/why not?

Sir Richie McCaw?

How could we gather views of all NZers?

Census? – pros/cons? … We take a sample

Homework…

Me as a mathematician…

Sampling methods

How could I select a group of you from a class list in order to check completion of homework?

Discuss different ways

that 5 students could be

selected

HANDOUT

Class list

Sampling methods

Notes…

Basic outline of each method they discussed

Simple random sampling

•Take a SRS of size 5 to select students to check their homework.

Systematic sampling

•Take a systematic sample of size 5 to select students to check their homework.

Why take a sample?

Purpose of sampling?

Reasons for sampling?

Features of a good sample?

Why take a sample?

The purpose of taking a sample is To make an estimate of what is going on

back in the population Reasons for sampling include

Time and cost considerations Lack of access to the entire population Nature of the data collection or test (eg

blood test, breaking strain of fishing lines…)

Why take a sample?

Features of a good sample Representative of the population Sample size is sufficiently large – a small sample

is more likely to be unusual and less likely to be representative

NOTE: there is no statistical requirement that a sample be a proportion of the population – a well designed sampling process is more likely to produce a representative sample than a large sample poorly selected

Randomly chosen – each member of the population has the same chance of being included in the sample