NCEA+Level+2+Sampling

=Practise Internals from= [] Mayor's Claim: Picking Fruit:

=Sampling Basics=

A simple random sample is unbiased. Advantages: speed, Disadvantages: minority groups may not be proportionally represented. A sample has "n" pieces of data (30?) Averages: measure central tendacy: mean (add values together, divide by n), mode (most common), median (middle value), Measures of spread: range, interquartile range, [could use a stem and leaf plot to order and view data] and standard deviation [tricky without a flash calculator]. Use your sample statistics to make estimates about the population. Remember: if your sample is representative, the sample statistics will be very close to those of the whole population.

For Merit, stating that your sample is a random sample is not sufficient to show that it is representative of the population. You need to link your sample to the relevant features of the population and consider bias.

Achievement with Excellence must relate to the sampling process you have used and considerations of ways in which this could be improved. (I used simple random, but stratified random would have been better because….)

[] Some good revision links here: http://2011maths.wikispaces.com/NCEA+Level+1+MV+Statistics

=Simple random sample: each boat has the same chance of being chosen.= Generate random numbers by entering “1+150RND#” into your calculator and truncating after the decimal point. For each random number generated find the boat allocated that number. Highlight the boat so you know it has been selected. Record the number of people in it. Ignore repeats. Continue until you have a sample of 30 Boats.

[] The conclusion of a statistical inference is a statistical Proposition. We make an estimate: An intelligent 'guess' drawn from our sample statistics.

You must reword for context of the question.
Example: the population is 150 boats on the harbour, your sample is of 30 boats with a mean of 4 people per boat. My sample of 30 boats has on average (mean) 4 people per boat, and it is a representative sample of the 150 boats, therefore, I estimate that the mean number of people per boat for the 150 boats is also 4. I therefore estimate that there are 600 people on the 150 boats.

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Go to [] and click on links for each text, click on theta. __ [] __