1. 9th Grade Making sense of data

2. How do we make sense of data?
Using graphs and tables
Calculating averages and variance (spread)
We can identify patterns and outliers in different test groups
This gives us ideas about the correlation (relationship) between our variables…

3. How do we make sense of data?calculations and thinking…
‘Average’: mean, median, mode
‘Error bars’: Variance, standard deviation, standard error of the mean, (interquartile range)
The relationship of causation and correlation
Classic graphs

4. In science, data are often normally distributed
Height
Blood pressure
Heart rate
Marks on an exam
Errors in machine-made products

5. If NOT normally distributed, data may be skewed (or just jumbled!)

6. Making sense of data – an example…

7. A drug to lower blood cholesterol…
Researchers have developed a new drug (tetesterol) to lower serum cholesterol levels
They treat 2 groups for a month with either tetesterol or placebo (no drug)
After 1month, the researchers measure cholesterol in both groups

8. Did the drug make a difference?
Cholesterol concentration after 1 month

9. First, ‘eyeball’ the data

10. Measure the AVERAGE (central tendency) (mean, median, mode)

11. Does calculating the mean provide us with enough information to see if the drug works?

12. Did the drug make a difference?
Cholesterol concentration after 1 month

13. Why not just look at the average?
The average may show a difference, but we can’t be sure that it’s a reliable difference Which of these data sets shows the greatest variation?

14. Is this difference reliable?
(i.e., does the drug
really make a difference?)
Cholesterol concentration
after 1 month

15. To properly compare test samples, we also need to look at the spread of the results We show this on graphs using ERROR BARS

16. Error bars on graphs
They are graphical representations of the spread (variability) of the data
Commonly represent:
Range
Standard deviation

17. Range – and its limitations

18. Standard deviation σ A measure of spread
It gives us an idea of the spread of most of the data and is much more reliable than range
You don’t need to know the formula
(You just need to press a button to calculate it)

19. Question check: Which data set has the highest mean?
Which data set has the highest variability?
What do the error bars represent?

21. Question check:

22. Correlations and coincidences

24. Positive correlation
The two variables measured change in the same direction
E.g. as temperature increases, the number of ice creams sold in Sara-Li’s increases

25. Lines of best fit Aim to draw a line that goes through
as many points as possible,
OR has an even number of points on either side
Sometimes there is NO line of best fit!

26. Negative correlation
As the number of weeks in the charts increases, the number of records sold falls

27. No correlation

28. Correlation doesn’t mean causation
Scientists often report correlations (associations) between two variables (e.g. body weight and sugar consumption; drug consumption and death; hours of sleep and exam performance)
Data are typically plotted as a scatter plot
Correlations DO NOT PROVE a cause.

29. How would you describe this relationship?
Positive correlation/ direct relationship
Negative correlation/ inverse relationship
Non-linear association
No association

30. How would you describe this relationship?
Positive correlation/ direct relationship
Negative correlation/ inverse relationship
Non-linear association
No association

31. How would you describe this relationship
Positive correlation/ direct relationship
Negative correlation/ inverse relationship
Non-linear association
No association

32. How would you describe this relationship?
Positive correlation/ direct relationship
Negative correlation/ inverse relationship
Non-linear association
No association

33. How would you describe this relationship?
Positive correlation/ direct relationship
Negative correlation/ inverse relationship
Non-linear association
No association

34. Which statement is most accurate?
As age increased, internet use always increased
Internet use was highest between 20 and 35
Neither of the above

35. Cities with higher population densities tended to have higher rents
Cities with higher population densities tended to have lower rents
There was no clear relationship between population density and rent

36. Larger groups tended to take more time to solve puzzle
Larger groups tended to take less time to solve puzzle
There was no clear relationship between group size and time to solve puzzle

37. Question check:

38. Question check: