3.3 COLLECT & ORGANIZE DATA

GATHERING DATA It’s important to gather accurate data and

to ensure the data is as complete as possible If you gather the data yourself, it is Primary

Data If you use data collected by others, it is

Secondary Data Might be errors in the published secondary

data Results might not state how data was

gathered, or limitations of the use of the data

“PRACTICE MAKES PERFECT”Come as close as you can to the centre of the circle by writing numbers for each attempt:

Attempt

Distance from Centre (cm)

1

2

3

4

5

“PRACTICE MAKES PERFECT” Let’s create a scatter plot from our data

to see if “practice makes perfect”

Dis

tance

fro

m

centr

e

Number of Attempts

Attempt

Distance from Centre (cm)

1

2

3

4

5

“PRACTICE MAKES PERFECT” Positive or negative correlation or

neither?

“PRACTICE MAKES PERFECT”

You would theoretically get a negative correlation

In other words, your first attempt would be at a large distance from the centre, and your subsequent attempts would result in the distances getting smaller and smallerer

ANALYZING DATA USING A SCATTER PLOTDavis conducted an experiment comparing a person’s leg length and how long it takes the same person to walk 100m. He gathered these data showing (leg length in cm, time taken in s).

(80,66), (73,74), (60,83), (64,62), (63,75), (78,76), (83,64), (54,81), (71,70), (78,76).a) Graph the data.b) Does the graph suggest a relationship

between leg length and time taken to walk 100m? If so, describe the relationship.

100M WALKING EXPERIMENT

50 55 60 65 70 75 80 850

10

20

30

40

50

60

70

80

90

Walking 100m

Distance (m)

Tim

e (

s)

a) Graph the data.

100M WALKING EXPERIMENT

50 55 60 65 70 75 80 850

10

20

30

40

50

60

70

80

90

Walking 100m

Distance (m)

Tim

e (

s)

b) Does the graph suggest a relationship between leg length and time taken to walk 100m? If so, describe the relationship.

>The points go down to the right. This suggests a negative

correlation.>Time taken to

walk 100m decreases as leg length increases

100M WALKING EXPERIMENT

50 55 60 65 70 75 80 850

10

20

30

40

50

60

70

80

90

Walking 100m

Distance (m)

Tim

e (

s)

>A point with first coordinate 85 might have a

second coordinate of 63.>So, someone with leg length

85cm might take about 63s to walk 100m.

c) Use the scatter plot to estimate the time it would take a person with leg length 85cm to walk 100m. Explain.

100M WALKING EXPERIMENT

More data would make Davis’ results more reliable. He could

recruit people with a wider range of leg lengths while keeping other factors, such as age, gender, and

body type, very similar.

d) How might Davis make the results of his experiment more reliable?

3.3 HOMEWORK p. 165 #1, 2, 3, 4