In your day-to-day life, you might have come across information, such as:
(a) Runs made by a batsman in the last 10 test matches.
(b) Number of wickets taken by a bowler in the last 10 ODIs.
(c) Marks scored by the students of your class in the Mathematics unit test.
(d) Number of story books read by each of your friends etc.
The information collected in all such cases is called data. Data is usually collected in the context of a situation that we want to study. For example, a teacher may like to know the average height of students in her class. To find this, she will write the heights of all the students in her class, organise the data in a systematic manner and then interpret it accordingly.
Usually, data available to us is in an unorganised form called raw data. To draw meaningful inferences, we need to organise the data systematically. For example, a group of students was asked for their favourite subject. The results were as listed below: Art, Mathematics, Science, English, Mathematics, Art, English, Mathematics, English, Art, Science, Art, Science, Science, Mathematics, Art, English, Art, Science, Mathematics, Science, Art. Which is the most liked subject and the one least liked?
The data regarding choice of subjects showed the occurrence of each of the entries several
times. For example, Art is liked by 7 students, Mathematics is liked by 5 students and so
on (Table 5.1). This information can be displayed graphically using a pictograph or a
bargraph. Sometimes, however, we have to deal with a large data. For example, consider
the following marks (out of 50) obtained in Mathematics by 60 students of Class VIII:Have you ever come across data represented in circular form The time spent by a child during a day Age groups of people in a town.
5.4.1 Drawing pie charts The favourite flavours of ice-creams for students of a school is given in percentages.
Sometimes it happens that during rainy season, you carry a raincoat every day
and it does not rain for many days. However, by chance, one day you forget to
take the raincoat and it rains heavily on that day.
Sometimes it so happens that a student prepares 4 chapters out of 5, very well
for a test. But a major question is asked from the chapter that she left unprepared.
Everyone knows that a particular train runs in time but the day you reach
well in time it is late!
You face a lot of situations such as these where you take a chance and it
does not go the way you want it to. Can you give some more examples? These
are examples where the chances of a certain thing happening or not happening
are not equal. The chances of the train being in time or being late are not the
same. When you buy a ticket which is wait listed, you do take a chance. You
hope that it might get confirmed by the time you travel.
We however, consider here certain experiments whose results have an equal chance
5.5.1 Getting a result You might have seen that before a cricket match starts, captains of the two teams go out to toss a coin to decide which team will bat first. What are the possible results you get when a coin is tossed? Of course, Head or Tail. Imagine that you are the captain of one team and your friend is the captain of the other team. You toss a coin and ask your friend to make the call. Can you control the result of the toss? Can you get a head if you want one? Or a tail if you want that? No, that is not possible. Such an experiment is called a random experiment. Head or Tail are the two outcomes of this experiment.