Title: Making Predictions
1Making Predictions
- Predict the actions of a larger group using a
sample
2Definitions
- Survey a method of collecting information
- Population the group being studied
- Sample a small part of the group or population
- Random Selected without preference
3How many students in this school are left-handed?
- To answer that question we could
- Ask every student in the school OR
- We could survey a small random sample
If our sample is random it should be
representative of the population.
4Our Survey
- Question Do you write left-handed or
right-handed? - Population All students at SDMS
- Sample Mr. Lovells 6th grade math class
- Is Mr. Lovells Math class a good choice?
- Selected without preference?
- Representative of the population?
- Large enough group to provide reliable data
5Make a prediction about the population
Based on the results of your survey, you can make
a prediction about the whole school.
Suppose 5 out of 20 students are left-handed.
The probability that a student is left-handed is
6Our prediction
If the probability of a student being left-handed
is ¼ THEN ¼ of the population should be
left-handed.
There are 960 students at SDMS SO ¼ of 960 is
240Our predictions is
7There are 240 left-handed students at SDMS
- If our sample is random, our prediction should be
fairly accurate!
8Determine a good Sample
- Every 9th person entering a grocery store is
asked to state their choice in an upcoming
election. - One hundred people in an Italian restaurant are
asked their favorite type of restaurant. - Every 5th person attending a WMHS basketball game
is asked their favorite High School
9Good Sample?
- Every 20th person leaving school is asked if they
pack their lunch or buy a school lunch. - Five people at a soccer match are asked their
favorite sport.
10Which Sample is Best?
Question Who is your favorite movie star?
- Ask people standing in line waiting to see a
movie - Ask people at a local shopping center
11Survey and Prediction
Lauren asked every 4th student on an alphabetical
list of the Dream Team to name their favorite
pizza topping
12What is the probability that a student likes
Meat-lovers pizza?
13P(Meat-lovers) 5/25 or 1/5
14Prediction
If there are 300 6th grade students, how many
probably like meat-lovers pizza?
What is 1/5 of 300?
15We predict that 60 students will prefer
meat-lovers Pizza.
16Remember to conduct a survey
- What is your population what group do you want
to know about - How do you pick your sample
- Is your sample random meaning picked without
preference, representative of the population and
big enough to provide accurate data.