Additional Questions (For Practice) - 12 | Chapter 4 : Statistics | CBSE Class 9 Maths
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Interactive Audio Lesson

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Understanding Daily Wages Data

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Teacher
Teacher

Today, we're going to analyze the daily wages of workers in a factory. The data shows how many workers earn within specific wage ranges. Who can tell me why it's important to calculate the mean daily wage?

Student 1
Student 1

To find out what the average worker is earning?

Teacher
Teacher

Exactly! Calculating the mean helps us understand the overall earnings. Let's take a look at the wage distribution: β‚Ή100-120 has 10 workers, β‚Ή120-140 has 20, β‚Ή140-160 has 30, and so on. How would we calculate the mean based on this data?

Student 2
Student 2

We need to multiply each wage range's midpoint by the number of workers in that range, then sum them up and divide by the total number of workers.

Teacher
Teacher

Right! So, remember the formula for the mean: Mean = Ξ£(fα΅’ * xα΅’) / N. Let's solve this problem together.

Finding the Mode from Family Data

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Teacher
Teacher

In the next exercise, we have data showing the number of children in 50 families. Can someone tell me what the mode is?

Student 3
Student 3

It's the number that appears most frequently, right?

Teacher
Teacher

Exactly! If we list out the number of children, we can identify which value occurs the most often. Let's tally them now!

Student 4
Student 4

So, if we see '2' appears 14 times, that means the mode is 2!

Teacher
Teacher

Well done! Understanding the mode helps us identify the most common occurrence in a dataset.

Constructing Frequency Distribution Tables

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Teacher
Teacher

Now let's focus on constructing frequency distribution tables. The blood groups of 30 students are provided. How do we start creating a frequency table?

Student 1
Student 1

We should count how many times each blood group appears.

Teacher
Teacher

Correct! Let's record the frequency next to each blood type and analyze our findings. What do you think will be the most common blood group?

Student 2
Student 2

Whichever has the highest count in our table!

Teacher
Teacher

Perfect! Don't forget to check for the least common as well, which allows us to draw interesting conclusions about the data.

Exploring Grouped Data

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Teacher
Teacher

Let’s think about the data on engineers' commute distances. Why do we group data like this?

Student 3
Student 3

It makes it easier to understand the range of distances, right?

Teacher
Teacher

Exactly! By grouping, we can quickly see how many engineers live within specific distance ranges. This can help urban planners in many ways.

Student 4
Student 4

And we can make histograms from it too!

Teacher
Teacher

Yes! Histograms provide a visual representation, which can be very useful for presentations.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section contains additional questions and exercises to practice statistical concepts, including data collection and analysis.

Standard

The section provides a series of practice questions that reinforce the understanding of key statistical concepts, such as mean, median, mode, along with data representation methods like frequency distribution tables. These exercises vary in difficulty and cover a range of practical applications.

Detailed

In this section, students are provided with a variety of practice questions to deepen their understanding of statistical analysis and data interpretation. The questions encourage the application of concepts learned in statistics, including the calculation of mean, median, and mode, as well as the creation and interpretation of frequency distribution tables. Students are tasked with representing data in graphical forms and analyzing real-world scenarios that require statistical reasoning. Overall, this practice aims to enhance the students' skills in handling data and applying statistical methods effectively.

Audio Book

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Mean Daily Wage Calculation

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  1. The following table shows the daily wages of workers in a factory:
Daily wages (β‚Ή) 100-120 120-140 140-160 160-180 180-200
No. of workers 10 20 30 15 5

Calculate the mean daily wage.

Detailed Explanation

To calculate the mean daily wage, you first need to find the mid-point for each wage range. Then, multiply these mid-points by the number of workers in each range and sum these products. Finally, divide this total by the total number of workers. The formula is:

Mean = (Ξ£(mid-point Γ— number of workers)) / Total number of workers.

Let's compute the mid-points:
- For 100-120: Mid-point = (100 + 120) / 2 = 110
- For 120-140: Mid-point = 130
- For 140-160: Mid-point = 150
- For 160-180: Mid-point = 170
- For 180-200: Mid-point = 190

Now calculate:
- Total = (110 Γ— 10) + (130 Γ— 20) + (150 Γ— 30) + (170 Γ— 15) + (190 Γ— 5)
- = 1100 + 2600 + 4500 + 2550 + 950 = 11500.
- Total number of workers = 10 + 20 + 30 + 15 + 5 = 80.
- Mean = 11500 / 80 = 143.75.

Examples & Analogies

Imagine you're calculating the average amount of money you spend on coffee every week. You note down each coffee purchase and its cost. By finding the average, you gain insights into your spending habits, just like finding the mean daily wage helps the factory understand wage distribution.

Finding the Mode

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  1. The following data gives the number of children in 50 families:

1, 2, 3, 0, 1, 2, 3, 4, 2, 1, 0, 2, 1, 2, 3, 4, 3, 2, 1, 0, 1, 2, 3, 4, 2, 1, 0, 2, 1, 2, 3, 4, 3, 2, 1, 0, 1, 2, 3, 4, 2, 1, 0, 2, 1, 2, 3, 4, 3, 2.

Find the mode of this data.

Detailed Explanation

The mode is the number that appears most frequently in a dataset. To find the mode of this data, count how many times each number (0, 1, 2, 3, 4) occurs:
- 0 appears 6 times
- 1 appears 8 times
- 2 appears 11 times
- 3 appears 8 times
- 4 appears 6 times

The number that occurs the most is 2, making it the mode of this dataset.

Examples & Analogies

Think of this like a popularity contest where you want to find out which book among your friends is the most liked. If most of your friends choose "Harry Potter," then that’s the mode of your group’s favorite books. In this example, the mode gives insight into common trends.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Mean: The average of a set of values.

  • Median: The central value of a dataset.

  • Mode: The value that occurs most frequently.

  • Frequency Distribution Table: A table that summarizes data by showing the frequency of various outcomes.

  • Histogram: A bar graph representing frequency, typically with no gaps between the bars.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Finding the mean of 10 scores: Sum of scores divided by 10.

  • Creating a frequency table for a dataset of student blood types, counting occurrences.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • To find the mean, sum and divide, for the most common, the mode will guide.

πŸ“– Fascinating Stories

  • Imagine a festival where kids win candies. The most candies one kid wins becomes the 'Mode'. The average candies kids have is the 'Mean'.

🧠 Other Memory Gems

  • MMMD for Mean, Median, Mode, Data. Remember the top three concepts!

🎯 Super Acronyms

F for Frequency. Use to remember how often data occurs.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Mean

    Definition:

    The average value of a dataset, calculated by summing all observations and dividing by the number of observations.

  • Term: Median

    Definition:

    The middle value of a dataset when arranged in ascending or descending order.

  • Term: Mode

    Definition:

    The value that appears most frequently in a dataset.

  • Term: Frequency Distribution Table

    Definition:

    A table that displays the frequency of various outcomes in a dataset.

  • Term: Histogram

    Definition:

    A graphical representation of data where bars are used to display the frequency of data within certain intervals.