PPDAC Cycle

What is the PPDAC cycle? The PPDAC cycle is a way of answering statistics questions. Each letter stands for one step. P = D = A = C = Problem Plan Data Analysis Conclusions / Comments

Problem To use the PPDAC cycle you need to state a problem or question. A suitable problem needs: to be answerable with the data obtained, It is clear who the problem is about. We know what numbers we need

Examples of summary questions. I wonder what are the typical heights of Year12 students at HGHS in 2013. I wonder what are the typical number of people in the house for Year12 students at HGHS in 2013. Examples of comparison questions. I wonder if Year 12 students at HGHS in 2013 tend to have a larger neck circumference than Year 10 students at HGHS in 2013.

Plan You need to show a clear explanation of why the particular sampling method has been chosen Sampling method means how you chose the people to measure.

For example: I have chosen to take a simple random sample For example: I have chosen to take a simple random sample. I have taken my random sample by drawing name cards out of a bag. This method will provide me with a sample of heights where every Year 12 student at this school had an equal chance of being selected. The sample should therefore be representative of all the Year12 students at this school.

Data Choose at least 30 from each group.

For example: The student has listed the 30 students they selected from all the Year12 students. They have included all of the variables available.

Analysis Draw dot plots or stem and leaf tables to organise the data. Draw box and whisker graphs if you need to compare groups. Use SSUMO to analyse the graphs.

First draw a dot plot to give a very simple overview of the data First draw a dot plot to give a very simple overview of the data. From this graph features such as the shape or distribution of the data can be described. Also comments about spread, the middle group (or groups) and anything unusual can be noted. A box plot visually gives more information especially in comparison situations. The box plot gives a good indication of the range, the inter-quartile range and where the middle 50% (box) of the data lies. It is recommended that the associated dot plot is kept with the box plot.

Conclusions / Comments Your conclusion must answer the problem. Re-write your problem as an answer.

e.g. Based on these data it seems that Year 10 boys were on average taller than the Year 10 girls. The median height and mean height for the boys was 170 cm compared with the median height and mean height for girls of 164 cm. This suggests that boys are on average about 6 cm taller than girls in Grade 10. There is a small amount of overlap between the middle 50% of height values. This small overlap supports the conclusion that boys are on average taller than girls. Also 75% of the boys are taller than 50% of the girls.

Extra Conclusions To write a better conclusion you may want to add extra information about: 1. Anything that might have gone wrong 2. Any way to improve your investigation. 3. Any extra information you got from your graphs.

e.g. From our sample we could not say that it was likely that boys in the 2011 censusatschool database had heavier schoolbags than girls in the 2011 censusatschool database. However the DBM was only 20grams below 1/3 of the OVS. To check our conclusion I would recommend that we take a larger sample of 100 students. This would mean there is less variability in the sample, because it is larger, and therefore our conclusion could be made more reliable. From my results It could be recommended that if the government makes bag weight limits they should be the same for boys and girls.