Statistics Class: Frequency Tables
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Questions and Answers

What is the range of the masses of the pineapples?

500 g

What is the formula to find the range of the masses of the pineapples?

Midpoint of the highest class – midpoint of the lowest class

How many pineapples have a mass between 500 g and 599 g?

12

What is the cumulative frequency of pineapples with a mass less than or equal to 699 g?

<p>60</p> Signup and view all the answers

How many pineapples have a mass greater than 800 g?

<p>22</p> Signup and view all the answers

What is the interquartile range (IQR) of the masses of the pineapples?

<p>Q3 – Q1</p> Signup and view all the answers

How can the interquartile range of a set of grouped data be determined from an ogive?

<p>By finding Q1 and Q3 first</p> Signup and view all the answers

What is the midpoint of the class 400 – 499?

<p>449.5</p> Signup and view all the answers

What is the midpoint of the class 900 – 999?

<p>949.5</p> Signup and view all the answers

How many pineapples have a mass less than or equal to 599 g?

<p>18</p> Signup and view all the answers

Study Notes

Constructing a Frequency Table

  • To construct a frequency table, first find the largest and smallest data values.
  • Calculate the size of each class interval by dividing the range of data values by the number of classes.
  • Determine the class intervals using the size of each class interval.
  • Create the frequency table with columns for height (or other variable), frequency, lower limit, upper limit, midpoint, lower boundary, and upper boundary.

Calculating Midpoint, Lower Boundary, and Upper Boundary

  • Midpoint = (lower limit + upper limit) / 2
  • Lower boundary = lower limit - 0.5
  • Upper boundary = upper limit + 0.5

Measures of Dispersion for Grouped Data

  • Dispersion can be calculated using two methods.
  • To compare the dispersions of two groups, calculate the range or interquartile range for each group.

Traffic Flow Survey

  • The diagram shows the survey results of traffic flow in two different locations.
  • The distribution shapes in both locations can be determined by examining the graph.
  • The dispersions of car speeds in both locations can be compared by calculating the range or interquartile range.

Constructing an Ogive

  • An ogive is a cumulative frequency graph.
  • To construct an ogive, first create a frequency table with cumulative frequencies.
  • Plot the cumulative frequencies against the upper boundaries of the class intervals.

Calculating Quartiles from an Ogive

  • To find the first quartile (Q1), draw a horizontal line from the axis of cumulative frequency at 25% until it intersects the ogive, then draw a vertical line down to find the value of Q1.
  • Repeat the process to find the second quartile (Q2) and third quartile (Q3).
  • Interquartile range = Q3 - Q1.

Calculating Range

  • Range = midpoint of the highest class - midpoint of the lowest class.
  • Range can be used to measure the dispersion of a set of grouped data.

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Description

Construct a frequency table based on raw data, including finding the lower limit, upper limit, midpoint, lower boundary, and upper boundary. Learn how to organize data into classes and calculate class intervals.

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