Grade 7Mathematics

Data Handling

Collecting, organising, presenting data; bar graphs, line graphs, pie charts; mean, mode, median.

📖 4 min read · 3 worked examples · 8 practice questions

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The lesson

Today we're starting our journey into Data Handling, a key skill that helps us make sense of the numbers around us. First, let's define data handling: it's the process of collecting, organizing, displaying, and interpreting information so we can answer questions and solve problems. Why does this matter? Think about the market price of maize in your town. By recording daily prices, we can spot trends, decide the best day to sell, and even help families plan their budgets. Another everyday example is school attendance records. When we organise that data, we can see patterns—like which days have lower attendance—and take action to improve learning. Our learning objectives for today are: 1) understand what data handling is, 2) recognise real‑world Kenyan examples, and 3) see how we will use these ideas throughout the term. If anyone has a quick example from home—maybe a family budget or a sports score—please share it now so we can connect it to data handling.

Everyone, let's dive into today's topic: presenting data using bar graphs. First, we need to remember the key parts of any graph: the axes, clear labels, a descriptive title, and appropriate scales. Notice this bar chart on the screen. The vertical axis shows sales amount, while the horizontal axis lists the fruit types sold at the Nairobi market. Each bar's height corresponds to the amount of sales, and we label each bar so anyone can see which fruit it represents. Notice the shape highlighting the difference between vertical and horizontal bars—vertical bars are great for comparing quantities, while horizontal bars work well when you have long category names. To recap, a clear title, labeled axes, proper scales, and thoughtful orientation help make a bar graph easy to read. Any questions before we move on?

Everyone, let's wrap up what we've learned today with a quick recap and look ahead to our next steps. First, we reviewed how to collect reliable data, the different types of graphs we can use, and how to find the central tendency—mean, median, and mode. Remember, accurate data handling means measuring carefully, recording every observation, and checking your numbers before you graph them. For homework, I'd like each of you to gather real data from home or your community—maybe the number of chickens on a farm or the amount of water used each day—and present it with one of the graph types we practiced. If you run into any challenges, feel free to ask me or the assistant during class tomorrow. Great work today, and I'm excited to see your graphs!

Worked examples

Presenting Data – Line Graphs

Let's explore line graphs, a powerful way to show how something changes over time. First, we connect each data point with a straight line. This helps us see the overall trend clearly. At this line chart. Notice how the slope tells us whether values are rising, falling, or staying steady. Our example shows rainfall in Kisumu over six months. As the line goes up, rain is increasing; when it dips, rainfall decreases. Any questions so far? Remember, a line graph is best when you want to track changes continuously, like temperature, distance, or monthly rainfall.

Presenting Data – Pie Charts

Let's talk about presenting data using pie charts. A pie chart helps us see how different parts make up a whole. Here's the pie chart we'll be working with. Each slice represents a sector of the data, and the size of each slice shows its percentage of the total. To find the percentage for each sector, we use this formula: Sector % equals the sector value divided by the total, multiplied by 100. First, we calculate the percentages for each sector, then we label each slice clearly so everyone can read the chart easily. We'll calculate each source's share and add labels to the chart.

Measures of Central Tendency

Everyone, let's dive into our new topic: Measures of Central Tendency. First, the mean – you add up all the numbers in a data set and divide by how many items there are. For example, if three farms yield 10, 15, and 20 tonnes of maize, the mean yield is (10 + 15 + 20) ÷ 3 = 15 tonnes. Next, the median – arrange the numbers in order and pick the middle one. Using the same yields sorted as 10, 15, 20, the median is 15 tonnes. Finally, the mode – the value that appears most often. If another farm also produced 15 tonnes, then 15 becomes the mode. We'll choose which measure to use depending on the situation: the mean for overall average, the median when data are skewed, and the mode for the most common outcome, like the most popular item at a school market day. Great, that's the core of today's lesson. Any questions before we move on?

Practice questions

  • For the first question, remember that the horizontal axis of a line graph always shows the categories that change over time – in this case the months. The correct label is "Months of the year.
  • The second question asks about the overall trend from January to June. At how the line moves: it rises steadily, meaning attendance increases month by month.
  • For the first question, add up the five weekly maize prices (45 + 50 + 55 + 50 + 60 = 260) and then divide by the number of weeks, 5. That gives a mean of 52 Ksh per kilogram.
  • The second question asks for the mode of the test scores. For the value that appears most often.
  • In the third question, compare the frequencies of the favorite sports: football 12, athletics 8, basketball 5, rugby 5. The highest count is football with 12 pupils, making football the mode of this list.
  • First, **Q1** asks you to create a bar graph from the agricultural data we examined earlier. Recall how we choose appropriate axes and label each bar clearly.
  • **Q2** focuses on interpreting a line graph of temperature changes. Think about the slope, the direction of the line, and what that tells us about warming or cooling trends.
  • For **Q3**, you'll draw a pie chart showing household water sources. Remember each slice must represent a proportion of the whole, and the percentages should add up to 100.

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