Stage 1 Statistics students from Auckland university

Sampling variability &the effect of sample size

Recap from last week…

1. What is PPDAC short for?2. What are three types of

investigative questions?3. What does a good investigative

question need to have?4. Give two reasons we might take a

sample rather than look at the whole population

Recap from last week…

5. Give four words that could be used to describe the shape of a distribution

6. You and your neighbour both take a random sample from the same population. Your neighbour sees that your work is different from theirs and says that you must have done something wrong. What would you say to your neighbour?

7. What is “sampling error”?

Stage 1 Statistics Data Internet based survey Stage 1 students at

Auckland University in 2009

Students invited to complete the survey and gain 2 marks towards their first assignment, marked out of ten.

Problem

I wonder what the median weight of Stage 1 Statistics students at Auckland University is?

Plan

Simple random sample of 30 students please.

Data

SRS of 30 students

Analysis

Plot dot plot on axes Add box plot above Note the 5 point summary

{Minimum, lower quartile, median, upper quartile, maximum}

Analysis

We’ll come back in a minute here and compare our n = 15 with our n = 30 distributions

Conclusion

EstimateParameterPopulationMedianDataSample

From my sample data, my best estimate of the population parameter is that the median weight for all Stage 1 statistics students is …This is a

Point estimate