Information and Data

In Unit 1 you met data: what a computer takes in and works on. Now we can be more exact, and tell data apart from information. Data means facts as they were written down or recorded, before anyone has made sense of them: numbers, words, measurements, answers to questions. On its own, data often tells you very little.

Look at this: 14, 12, 8, 4, 2. What does it mean? You can’t tell. It is just data.

Now: Of the 40 students in Class 6, 14 walk to school, 12 come by school bus, 8 by motorbike, 4 by bicycle and 2 by public bus. Now the same numbers mean something. When data has been organized and given meaning, so that it answers a question, it becomes information. And you can see at once that walking is the most common way to come.

A tea shop shows the difference well. Every order is written on a slip: “2 milk tea, 1 black tea, 7:15 a.m.” A day’s pile of slips is data. When the owner sorts and counts the slips and finds that milk tea sells twice as much as black tea in the morning, that is information. It helps her decide how much milk to buy.

Turning data into information is one of the things computers do best. It is Unit 1’s idea again: data goes in, the computer processes it (sorting, counting, adding, comparing), and information comes out.

To find out how your class comes to school, you have to ask. Asking a group of people the same questions and recording their answers is called a survey. Each person who answers is a respondent.

A survey is only as good as its questions. Look at what happens if you just ask, “How do you come to school?” and write down whatever people say:

“Walking.” “On foot.” “Bike.” “My dad drops me.” “Sometimes bus, sometimes walk.”

“Walking” and “on foot” are the same, but they are written differently, so a computer will count them separately. “Bike” could mean a bicycle or, as many people in Nepal say, a motorbike. “My dad drops me” doesn’t say how. And what about the student who does both?

A better survey gives answer choices: a short list of answers, and each person picks one.

How do you usually come to school? Tick one.
☐ Walk ☐ Bicycle ☐ Motorbike ☐ School bus ☐ Public bus or tempo ☐ Other

Good answer choices:

• Fit everyone. Every respondent can find their answer. An Other choice catches the ones you didn’t think of.
• Don’t overlap. Each person fits only one choice. (“Usually” helps the student who sometimes walks and sometimes takes the bus.)
• Mean one thing. “Motorbike”, not “bike”.

A good question is also fair: it doesn’t push people towards one answer. “Don’t you agree that walking is the best way to come to school?” is a leading question: it tells people what to say. Ask, “How do you usually come to school?” and let them answer.

Recording the answers

The quickest way to count answers on paper is with tally marks: one stroke for each answer, and every fifth stroke drawn across the four before it, so the strokes come in easy-to-count bundles of five.

Asking kindly and safely

Data about people belongs to those people. When you run a survey:

• Ask only what you need. To find out how people travel, you don’t need anyone’s home address or phone number.
• Tell people what the survey is for, and let anyone say no.
• Keep the answers to yourself and your teacher. When you share results, share the counts (“14 students walk”), not who said what.

Here are the answers from ten students in Class 6, with two more questions added: about how far they live from school, and how many minutes the trip takes.

A table like this has a simple rule: one row for each thing, one column for each kind of fact about it.

• Each row holds everything about one student. A row like that is called a record. This table has 10 records.
• Each column holds one kind of fact about every student: their names, or how far they live. A column like that is called a field. This table has 4 fields.
• The top row, the header row, gives each field its name. It isn’t a record.

Your school keeps tables like this: the attendance register has a row for each student and a column for each day. A shop’s billing computer, a phone’s contact list and the list of payments in a wallet app all keep data as records and fields too.

You could add up the minutes in that table with a pencil, or a calculator. But if one student changes their answer, you have to do it all again. A spreadsheet program does it for you, and does it again by itself whenever the data changes.

A spreadsheet is a big grid, like the squared pages of a math notebook.

• The columns are named by letters: A, B, C…
• The rows are numbered: 1, 2, 3…
• Each box in the grid is a cell. A cell is named by its column and then its row, like a seat in a cinema hall: the cell in column B, row 3, is B3. This name is the cell’s address.
• Above the grid, the formula bar shows exactly what is in the selected cell.

To fill in a spreadsheet, tap or click a cell and type. The header row goes in row 1, and each record in a row of its own underneath. Numbers line up on the right of their cells and words on the left. That is useful: if a number you typed sits on the left, the spreadsheet has read it as a word (perhaps you typed a letter by mistake, like the letter O for a zero, or added “km”).

Look again at the ten students. Who lives nearest the school? Who lives farthest? With ten records you can search with your eye. With four hundred, you can’t.

Sorting puts the records in order by one of the fields. You can sort:

• ascending: smallest to largest (1 → 9), or A to Z, or
• descending: largest to smallest (9 → 1), or Z to A.

Sorted by km ascending, the student who lives nearest comes first (Fulmaya, 0.5 km) and the one who lives farthest comes last (Gopal, 9 km). Sorted by Comes by from A to Z, all the bicycles come together, then the motorbikes, the school buses and the walkers, so they are easy to count.

Putting records with the same answer together, then counting or adding up each group, is called grouping. Your tally marks grouped the class by hand: one row of marks for each way of coming to school.

When a spreadsheet sorts, it moves whole rows. Gopal’s distance stays with Gopal’s name, his way of coming and his minutes. A record must never be split up.

Now let the spreadsheet do the sums. In a cell, you can type a formula: an instruction that works out a value. A formula always starts with =. Without the =, the spreadsheet thinks you typed a word.

The simplest formulas use cell addresses: =C2+C3 adds the numbers in C2 and C3. But adding a long column like that is slow. So spreadsheets have functions: ready-made instructions with a name, and the cells to work on in brackets.

A block of cells is written as its first and last cell with a colon between them: C2:C11 means every cell from C2 down to C11. That is called a range.

The cell shows the answer, and the formula bar shows the formula. Here is the best part: if Hira moves house and her trip becomes 25 minutes instead of 30, you change one cell, and the total and the average change by themselves.

A table holds the facts exactly. A chart shows them as a picture, so you see the pattern at a glance. Spreadsheets draw charts from a table in a few taps, and when a number in the table changes, the chart changes too.

Bar charts

A bar chart draws a bar for each group. The longer the bar, the bigger the number, so you can compare the groups at a glance. A bar chart has:

• a title that says what it shows,
• the groups along one axis (the line along the bottom), with the axis named (“Comes by”),
• a scale of numbers up the other axis, starting at 0, also named (“Students”).

Pie charts

A pie chart is a circle cut into slices, like a round cake shared out. The whole circle is everything (here, all 40 students), and each slice is one group’s share of it. The slices are often labeled with percentages: how many out of every hundred. 14 of the 40 students walk, and 14 ÷ 40 = 0.35, so walkers are 35% of the class: just over a third of the circle.

Which chart?

The two kinds of chart answer different questions.

• A bar chart is best for comparing amounts: which group is biggest, how much bigger. It also works when the numbers aren’t parts of one whole (the heights of mountains, the temperature each month) and when there are many groups.
• A pie chart is best for showing shares of one whole: what part of the class walks, how a family’s money is shared out. Its slices must add up to the whole, 100%. It works best with a few groups; with many, the slices get too thin to tell apart.

A chart can tell the truth about data, or it can mislead you, even when every number in it is right. Both charts below show exactly the same data: how many Class 6 students came to school by school bus in four years.

The number went from 11 to 14: three more students. That is a real change, but a small one. Yet the misleading chart makes it look as if bus riders had multiplied by four. Here is how it does that.

• The axis doesn’t start at 0. A bar chart works because the length of a bar stands for its number. Start the axis at 10 and every bar loses its first 10: the bar for 11 is cut down to a stub of 1, the bar for 14 to 4. Now one looks four times the other.
• The axis has no numbers. You can’t see that it starts at 10, so you can’t correct for it in your head.
• The title shouts. “Shoot up!” tells you what to think before you have looked.

A chart is honest when someone reading only the chart understands the data correctly. Before you trust a chart, or share one you made, check:

• Is there a title that says what is shown, and where and when?
• Are both axes named, with the units (students, km, rupees)?
• Does the bar chart’s axis start at 0?
• Does the axis have numbers, evenly spaced?
• Do a pie chart’s slices add up to 100%, one whole?
• Where did the data come from? Was it a fair survey?

If the answer to any of these is no, be careful: redraw the chart honestly, or read its numbers, not its shape.