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Describing Graphs

Describing Graphs. Using your knowledge to describe the features of graphs. For each sample make descriptive statements about- - Spread - Shape - IQR. Describing. You should ask yourself about how the data is spread out: What is the range? What is the IQR?

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Describing Graphs

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

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

  3. 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

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

  5. 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

  6. Skew- always describe the tail! Shape

  7. BOYS1 Spread? Shape?

  8. BOYS2 Shape? Spread?

  9. BOYS3 Spread? Shape?

  10. 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

  11. Shift • 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

  12. 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

  13. 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

  14. IQR??

  15. IQR?

  16. IQR?

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