## Lesson 8: Normal Curves

September 13, 2016

Wed, Sep 14

Review:

**Exam 1 will be on Wed, Sep 28**- Variance and Standard Deviation
- Why do we divide by n – 1?

Presentation:

- Density Curves
- Height of curve indicates proportion of values
- Area under the curve = 1.0
- Any sub-area under the curve is then a proportion (% of values)

- Normal Curves
- A special case of density curves
- Bell shaped and symmetrical
- Mean and Standard deviation
- 68 – 95 – 99.7 Rule
- Video

Activity:

- Problem 1.
- Height of 4-year-old boys is approximately normally distributed with mean 40 inches and standard deviation 1.5 inches.
- Draw a normal density curve and label the mean on the horizontal axis.
- Also mark points on the horizontal axis one standard deviation on either side of the mean.

- Height of 4-year-old boys is approximately normally distributed with mean 40 inches and standard deviation 1.5 inches.
- Problem 2.
- IQ scores are normally distributed with mean 100 and standard deviation 15. Scores from 90 to 110 represent normal or average intelligence. Scores above 120 represent superior intelligence.
- Draw a normal density curve for IQ scores.
- Label the mean and one standard deviation on either side of the mean.
- Shade the area under your normal curve that represents the proportion of people with normal intelligence.
- Then shade, in a different way, the area representing the proportion of people with superior intelligence.

- IQ scores are normally distributed with mean 100 and standard deviation 15. Scores from 90 to 110 represent normal or average intelligence. Scores above 120 represent superior intelligence.

Assignment:

- Read pp. 53-61 Density Curves and Normal Distributions
- Complete the Use Your Knowledge questions 1.99 and 1.100 on pp. 60-61