1. Unit 2
Research and Methods

2. Module 7 – Statistical Reasoning

3. Module 7 Objectives
SWBAT: discuss descriptive statistics SWBAT: discuss inferential statistics and why they can be generalized to other populations

4. Descriptive Stats Descriptive stats
Statistics that DESCRIBE a set of data
Involve mean, median, and mode
With your team, ID the mean, median, and mode on the graph below.
Student practice for mean, median, mode?

5. Descriptive Stats Skewed distribution
A situation where the scores/data is not evenly distributed around the mean
Based on the image from before, what could be causing this skewed distribution of scores?

6. Central Tendency vs. Variability
How did the others measure “central tendency”? (as in, mean, median, mode)
Variability tells us much, much more.
Standard Deviation:
How much do scores vary around the mean score?
Larger SD = scores vary wildly
Smaller SD = most scores are close to the mean

7. Standard Deviation
Looking at the image below, what is the mean for both?
Going off just the mean, what would you conclude about how each class is doing?
However, what are the standard deviation for each class?
What does that REALLY tell you about how the students in each class are doing? Are all students in class B doing well?

8. Standard Deviation
Looking at the image below, what is the mean for both?
Going off just the mean, what would you conclude about how each class is doing?
However, what are the standard deviation for each class?
What does that REALLY tell you about how the students in each class are doing? Are all students in class B doing well?
What’s causing Class B’s mean to be so high?

9. Grading on the Curve
Below is the normal curve – what kind of shape is it?
What does the “bell” form around?

10. Grading on the Curve Are most people average, or exceptional?
So if most scores are clustered lower than the mean, what does that tell you about the difficulty of the test?
If most scores are higher?

11. Inferential Statistics
Allow us to INFER MEANING from data
When is it meaningful?
Statistical significance –
The likelihood that you got your results due to chance
In psychology, this variable is called a “p-value”
P MUST BE LESS THAN 0.05
0.05 = likelihood due to chance less than 5% (95% likely due to treatment)

12. Inferential Statistics
LAST KEY POINT QUESTION:
What is the primary difference between descriptive and inferential statistics?
Why is it important that we have a low p-value?