Averages from a Grouped Frequency Table
Learn how to find the modal class, median class, and estimate the mean from a grouped frequency table. Let’s get started! 🚀
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Flashcards
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🛎️ What Is a Grouped Frequency Table?
- A grouped frequency table organises data into class intervals.
- Each class shows how many values fall within that interval.
🛎️ How to Find the Modal Class?
- The modal class is the class with the highest frequency.
- It shows where the data occurs most often.
🛎️ How to Find the Median Class?
- Add the frequencies to find the total number of values (n).
- Use (n + 1) ÷ 2 to find the median position.
- If n = 25, (25 + 1) ÷ 2 = 13, so the class containing the 13th value is the median class.
🛎️ How to Estimate the Mean?
- Find the midpoint of each class by adding the lower and upper values and dividing by 2.
- Multiply each midpoint by its frequency and add the results.
- Divide this sum by the total frequency to estimate the mean.
Practice Questions
Test your understanding
The table shows the ages of people attending a concert. How many people are represented in total?
Correct! 🎉 +10 pointsNot quite right
Add all the frequencies: people attended the concert.
The table shows the ages of people attending a concert. What is the modal class for the data?
Correct! 🎉 +10 pointsNot quite right
The modal class is the age group with the highest frequency. Here, 20-30 years has the highest frequency of 8 people.
The table below shows the delivery times for a courier service. Which class contains the median delivery time?
Correct! 🎉 +20 pointsNot quite right
First find the total frequency: . The median lies between the 10th and 11th values. Both of these fall in the 20-30 minute class, so this class contains the median delivery time.
What is the midpoint of the 20-30 minute interval?
Correct! 🎉 +20 pointsNot quite right
The midpoint of the 20-30 minute interval is calculated as .
If 2 more orders are added to the 30-40 minutes range, how will this affect the modal class?
Correct! 🎉 +20 pointsNot quite right
By adding 2 more orders to the 30-40 range, its frequency increases to 8, making it the highest frequency. The modal class becomes 30-40 minutes.
Using the table below, estimate the mean delivery time.
Correct! 🎉 +30 pointsNot quite right
Multiply each midpoint by its frequency: . Then divide by the total frequency: minutes.
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Averages from grouped frequency table
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