Using your knowledge to describe the features of graphs Describing Graphs Using your knowledge to describe the features of graphs

For each sample make descriptive statements about- - Spread - Shape - IQR Describing

Spread You should ask yourself about how the data is spread out: What is the range? What is the IQR? How big is the IQR compared to the range? Are the quarters even? You should be able to describe the situation using correct terminology. Spread

Generally we compare the data to a normal distribution (pictured below) Shape

To get an idea of shape you can sketch a rough outline of your distribution. Is the data grouped in certain locations? Is the data unimodal (is there one clear peak)? Is the data skewed? Shape

Skew- always describe the tail! Shape

BOYS1 Spread? Shape?

BOYS2 Shape? Spread?

BOYS3 Spread? Shape?

Inter-Quartile Range IQR is the middle 50% of the data- Its the box in the box and whisker plot! When we compare two subsets we need to compare the IQR’s to make a decision about differences in the population. If there is a significant separation we can infer a difference in populations. Inter-Quartile Range

Inter-Quartile Range Shift Overlap Is one IQR shifted further up/down the scale than the other? Overlap Is there any overlap of IQR’s? Quantify the overlap Inter-Quartile Range

Overall Visible Spread Overall Visible Spread is a VISUAL tool designed to help make decisions: Estimate the OVS You should sketch the OVS and cut it into sections depending on the size of the sample. If sample ≈ 30 then estimate thirds If sample ≈ 100 then estimate fifths If sample ≈ 1000 then estimate tenths. This can then be compared to the distance between the medians (DBM). Overall Visible Spread

DBM vs OVS Estimate the DMB just as you estimate the OVS. Sketch the distance between medians. Compare the DBM to the OVS visually- this is not a calculation. The calculation should only ever be used in extremely close situations. Make the call based on: If sample size ≈ 30 then DBM > 1/3 If sample size ≈ 100 then DMB > 1/5 If sample size ≈ 1000 then DBM > 1/10 DBM vs OVS

IQR??

IQR?

IQR?