MP Board Class 9th Maths Solutions Chapter 14 Statistics Ex 14.2
The blood groups of 30 students of Class VIII are recorded as follows:
A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O,
A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O.
Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students?
Frequency distribution table:
Common blood group – O
Rarest blood group – AB.
The distance (in km) of 40 engineers from their residence to their place of work were found as follows:
Construct a grouped frequency distribution table with class size 5 for the data given above taking the first interval as 0 – 5 (5 not included). What main features do you observe from this tabular representation?
Frequency distribution table:
We can observe that residence of most of the engineers are at a distance of 5 – 20 km from their place of work.
The relative humidity (in %) of a certain city for a month of 30 days was as follows:
- Construct a grouped frequency distribution table with classes 84 – 86, 86 – 88, etc.
- Which month or season do you think this data is about?
- What is the range of this data?
1. Frequency distribution table.
2. Rainy season as the relative humidity is high.
3. Range = 99.2 – 84.9 .
The heights of 50 students, measured to the nearest centimeters, have been found to be as follows:
- Represent the data given above by a grouped frequency distribution table, taking the class intervals as 160 -165,165 -170, etc.
- What can you conclude about their heights from the table?
1. Frequency distribution table
2. We observe that most of the students have their heights between 160 – 165 cm.
A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows:
- Make a grouped frequency distribution table for this data with class intervals as 0.00 – 0.04, 0.04 – 0.08, and so on.
- For how many days, was the concentration of sulphur dioxide more than 0.11 parts per million?
2. The concentration of sulphur dioxide was more than 0.11 ppm for 8 days.
Three coins were tossed 30 times simultaneously. Each time the number of heads occurring was noted down as follows:
Prepare a frequency distribution table for the data given above.
The value of n upto 50 decimal places is given below:
- Make a frequency distribution of the digits from 0 to 9 after the decimal point.
- What are the most and the least frequently occurring digits?
2. The most frequently occurring digits are 3 and 9. The least occurring is 0.
Thirty children were asked about the number of hours they watched TV programmes in the previous week. The results were found as follows:
- Make a grouped frequency distribution table for this data, taking class width 5 and one of the class intervals as 5 – 10.
- How many children watched television for 15 or more hours a week?
2. 2 children.
A company manufactures car batteries of a particular type.ffhe lives (in years) of 40 such batteries were recorded as follows:
Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the interval 2 – 2.5.