Primary & Secondary Data
This type of data is collected directly by the person doing the research.
Primary
Data that describes qualities or categories instead of numbers.
What is qualitative data?
This occurs when data is unfairly collected or presented to support a certain idea.
What is bias?
When the scale on a graph starts at a number other than zero to exaggerate differences, the graph may be this.
What is misleading?
This graph is best used to compare categories of data.
Bar
A researcher using census data collected by the government is using this type of data.
Secondary
Data that can be measured or counted with numbers.
What is quantitative data?
Surveying only basketball players about their favourite sport would create this problem.
What is bias?
The average of a dataset.In a frequency table, this column usually lists the categories or data values.
Mean
This graph is best used to show change over time.
Line graph
An example of collecting primary data in school would be this.
What is surveying classmates / conducting an experiment / making observations?
Favorite ice cream flavours collected from students would be this type of data.
What is qualitative data?
A survey asking “Don’t you agree that longer school lunches are better?” is an example of this.
What is a biased question?
A teacher recorded the number of minutes students read at home last night:
20, 25, 30, 30, 35, 40, 120
a) Find the mean.
b) Find the median.
c) Which measure best represents the typical reading time? Explain why.
a) Mean
Sum = 20 + 25 + 30 + 30 + 35 + 40 + 120 = 300
Mean = 300 ÷ 7 ≈ 42.9 minutes
b) Median
Ordered data: 20, 25, 30, 30, 35, 40, 120
Middle value = 30
Median = 30 minutes
c) Best measure
Median, because 120 is an outlier and makes the mean much larger than the typical reading time.
This graph shows parts of a whole using slices.
Circle
Explain the difference between primary and secondary data.
Primary data is collected firsthand, while secondary data is collected by someone else and reused.
The number of hours students spend studying each week is this type of data.
What is quantitative data?
Why is bias a problem when collecting data?
It makes results unfair or inaccurate.
A survey asked students their favourite school lunch.
Pizza - 12 students
Sandwich - 7 students
Pasta - 5 students
Salad - 3 students
a) Which measure of central tendency would best describe this data?
b) What is the answer?
a) Mode is the best measure because the data is categorical.
b) Pizza (12 students) is the mode.
Gr 8 - This graph groups numerical data into intervals or bins.
Histogram
A scientist reads data from a study published last year. What type of data are they using?
What is secondary data?
Name one example of qualitative data and one example of quantitative data.
Example answers:
Qualitative – favourite colour
Quantitative – height, age, number of pets
Give one way to reduce bias when collecting data.
• Survey a random group
• Ask neutral questions
• Include many different participants
These are the test scores from a small class:
75, 78, 80, 82, 84, 85, 87
a) Find the mean.
b) Find the median.
c) Which measure better represents the class performance? Explain.
Data: 75, 78, 80, 82, 84, 85, 87
a) Mean
Sum = 571
Mean = 571 ÷ 7 ≈ 81.6
b) Median
Middle value = 82
c) Best measure
Either mean or median works well because there are no outliers and the data is fairly evenly spread.
Gr 8 This graph shows the relationship between two variables.