Stats - Cumulative Frequency


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What goes on the $x$-axis on a cumulative frequency diagram?

The variable being measured.

What does on the $y$-axis on a cumulative frequency diagram?

Cumulative frequency.

What is the purpose of a cumulative frequency diagram?

It allows you to find estimates for medians, quartiles and percentiles.

Drawing a cumulative frequency diagram is like what other process in stats?

Linear interpolation.

When plotting a cumulative frequency diagram for grouped data, which class boundary should you use for the point on the $x$-axis?

The lower class boundary.

I have a cumulative frequency diagram with a max frequency of 60. I want to find an estimate for the upper quartile. What should I do?

  • $60 \div 4, \times 4 = 45$
  • Find $45$ on the $y$-axis, draw a straight line to the curve.
  • Draw a line from that point on the curve to the $x$-axis and that is the value.

How should you join the points on a cumulative frequency diagram?

With a smooth curve.




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