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1) Load the whole population Go to NZ Grapher  Import data  'paste table' 2) Taking a SampleThe sample is taken from the whole population, and we want to get at least 30 data values for each group, so a sample of say 80 is needed. 'Sample and more' > Sample with > add the sample sie of each group If there is a problem with your sample then 'restore the Data set' and repeat the sampling 

3) Greate dot & box plots Add variables  Graph type 'Dot plot (and box and whisker)' on the check boxes > boxplot & show summary statistics' 

4) Discuss...This gives the mean, median, mode etc of your sample. Remember each time you take a sample from a population the sample statistics (and the graphs) will be different (but similar)


5) Calculate the Informal Confidence Interval.Using the sample statistics from above, for each group you will need to find the informal confidence interval. This is the interval within which we can be reasonably sure the actual population median occurs. The concept of using sample statistice to determine an estimate of the population is the key idea. In level 3 statistics you will encounter situations where the population is unknown using NZgrapher 'show informal confidence interval' 
Sample Median +/ 1.5 x (Upper quartile  Lower Quartile) / sqrt(of the sample size n) For the female height example the calculation would be Lower Informal Confidence Interval limit = 159  1.5 x (165  152) / √41 = 155.5cm Upper Informal Confidence Interval limit = 159 + 1.5 x (165  152) / √33 = 162.4cm 

6) DiscussNow interpret the results. Do the intervals overlap? or not? What does this mean?


