# 9.1 Generalization and inference

Good morning!
Schedule:
• Revision quizz
• Homework discussion
• Generalization and inference
• Sample size
• New homework
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Slide 1: Slide
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This lesson contains 24 slides, with interactive quizzes and text slides.

## Items in this lesson

Good morning!
Schedule:
• Revision quizz
• Homework discussion
• Generalization and inference
• Sample size
• New homework

#### Slide 1 -Slide

Learning goals
At the end of this lessons I can:
• Identify what sampling method is being used
• Choose an appropriate sample size to make reliable Generalizations.

#### Slide 2 -Slide

Revision quiz!

Let's revise some vocabulary and the different sampling methods

#### Slide 3 -Slide

What is a Population?
A
A specific group of individuals where you collect data from.
B
A conclusion based on a sample.
C
A collection of data from every person in a research group.
D
The entire group you want to draw (statistical) conclusions about.

#### Slide 4 -Quiz

What is a Sample?
A
A specific group of individuals where you collect data from.
B
A conclusion based on a sample.
C
A collection of data from every person in a research group.
D
The entire group you want to draw (statistical) conclusions about.

#### Slide 5 -Quiz

What is Inference?
A
A specific group of individuals where you collect data from.
B
A conclusion based on a sample.
C
A collection of data from every person in a research group.
D
The entire group you want to draw (statistical) conclusions about.

#### Slide 6 -Quiz

What is a Census?
A
A specific group of individuals where you collect data from.
B
A conclusion based on a sample.
C
A collection of data from every person in a research group.
D
The entire group you want to draw (statistical) conclusions about.

#### Slide 7 -Quiz

What Sampling Method is being used?
You want to select a sample of 100 employees of Company X. You assign a number to every employee in the company database from 1 to 1000, and use a random number generator to select 100 numbers
A
Simple random sample
B
Systematic sample
C
Stratified sample
D
Quota sample

#### Slide 8 -Quiz

What Sampling Method is being used?
You want to select a sample of 100 employees of Company X. The company has 800 female employees and 200 male employees, you want your sample to have the same female/male distribution as the population. You separate the employees in 2 groups, male and female. Then you select 80 woman randomly from the female group and 20 men randomly from the male group.
A
Simple random sample
B
Systematic sample
C
Stratified sample
D
Quota sample

#### Slide 9 -Quiz

What Sampling Method is being used?
You want to select a sample of 100 employees of Company X. All employees are listed in alphabetical order. From the first 10 numbers  you randomly select a starting point: number 6. From number 6, every 10th person on the list is selected (6, 16, 26, 36, 46, and so on) until you have a sample of 100 people.
A
Simple random sample
B
Systematic sample
C
Stratified sample
D
Quota sample

#### Slide 10 -Quiz

What Sampling Method is being used?
You want to select a sample of 100 employees of Company X. The company has 800 female employees and 200 male employees, you want your sample to have the same female/male distribution as the population. You select random employees for your sample and note if they are male or female. When you have selected 80 females for your sample, you don't accept any more females in your sample (the same applies if you have 20 males in your sample).
A
Simple random sample
B
Systematic sample
C
Stratified sample
D
Quota sample

#### Slide 11 -Quiz

Homework
Discuss with your group any questions you might have from the homework.
If you are done or do not have any questions, discuss with your group what homework question was most difficult or challenging.

#### Slide 12 -Slide

Generalization and inference
Inference: A conclusion based on (statistical) facts with                                         evidence.

Generalization: Inferring the results from a sample and                                                     applying it to a population

#### Slide 13 -Slide

Generalization and inference

#### Slide 14 -Slide

Generalization and inference
What are the 2 populations from these samples?

What can we infer about the mean height of these populations?

What generalization can we make from the boy's heights in Antonia's year group?

#### Slide 15 -Slide

Sample size
Every group will calculate the average time spent on Mathematics homework with different sample sizes.

Who will be the closest to the actual average time spent?

#### Slide 16 -Slide

Sample 1
Time spent on Mathematics homework in minutes.

n = 20

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 17 -Slide

Sample 2
Time spent on Mathematics homework in minutes.

n = 12

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 18 -Slide

Sample 3
Time spent on Mathematics homework in minutes.

n = 6

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 19 -Slide

Sample 4
Time spent on Mathematics homework in minutes.

n = 32

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 20 -Slide

Sample 5
Time spent on Mathematics homework in minutes.

n = 18

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 21 -Slide

Sample 6
Time spent on Mathematics homework in minutes.

n = 27

Calculate the average (mean) time spent on Mathematics homework.

#### Slide 22 -Slide

Actual average
The average time spent on Mathematics homework ≈ 45.24 min

What can you infer about the average time spent on Mathematics homework in MP4?

What sample size would you choose if you wanted to make Generalizations about the average time spent on English homework?