2.9 Making an Inference AS 91264
For more information see the Nayland College website
Revising the PPDAC cycle
Problem
Analysis/Display
Calculations: median, quartiles, informal confidence interval
Graphs - dotplots and box and whisker plots
Describe what you see in the dot plots: discuss symmetry, skew, unusual values/outliers, gaps, clusters.
Describe the boxplots - shift, spread, overlap, middle 50%
ie. SHIFT: how much further up the x-axis is one box compared to the other.
SPREAD: how spread out the "boxes" are.
OVERLAP: how much the middle 50% (the "boxes") overlap.
Also consider possible reasons or causes of these features (in the context)Discussion of sampling variability, including the variability of estimates (ESSENTIAL )
Conclusion
For more information see the Nayland College website
Revising the PPDAC cycle
Problem
- investigate the variables - choose which ones to investigate
- define the problem
- write the investigation questions/hypothesis - make sure that this clearly defines your POPULATION
- main focus =comparison question
- Your Question MUST:
- Identify the variables, for example gender and height,
- Identify the population groups, for example NZ year 12 girls and NZ year 12 boys.
- Identify the population parameter -eg. the median
- eg. 'I wonder how the median height of NZ year 12 boys compares to the median height of NZ year 12 girls'. I expect that the boys will be about 15 cm taller.
- Define your chosen variables and explain why you have selected them. Explain the background context.
- Use common sense to write a concise summary of what you are going to do.
- include sampling method - SIMPLE RANDOM SAMPLING - ie state that it is simple random sampling and how this should provide a set of data representative of the population.
- Check/Clean the data if necessary.
Analysis/Display
Calculations: median, quartiles, informal confidence interval
Graphs - dotplots and box and whisker plots
Describe what you see in the dot plots: discuss symmetry, skew, unusual values/outliers, gaps, clusters.
Describe the boxplots - shift, spread, overlap, middle 50%
ie. SHIFT: how much further up the x-axis is one box compared to the other.
SPREAD: how spread out the "boxes" are.
OVERLAP: how much the middle 50% (the "boxes") overlap.
Also consider possible reasons or causes of these features (in the context)Discussion of sampling variability, including the variability of estimates (ESSENTIAL )
Conclusion
- Make a conclusion communicating your findings (answering your statistical comparison question, with mathematical justification.
- You must make an inference, which will be a conclusion about the population medians based on their samples taken from the population.
- Your conclusion will answer the posed investigative question and will involve making a call about the population medians.
- The informal confidence intervals will be used to make an inference about the population medians.