1. “Statistical unit is necessary not only for the collection of data, but also for the interpretation and presentation”. Explain the statement.
2. Find the standard deviation and coefficient of skewness for the following distribution
Variable

05

510

1015

1520

2025

2530

3035

3540

Frequency

2

5

7

13

21

16

8

3

3. A salesman has a 60% chance of making a sale to any one customer. The behaviour of successive customers is independent. If two customers A and B enter, what is the probability that the salesman will make a sale to A or B.
4. To verify whether a course in Research Methodology improved performance, a similar test was given to 12 participants before and after the course. The original marks and after the course marks are given below:
Original Marks

44

40

61

52

32

44

70

41

67

72

53

72

Marks after the course

53

38

69

57

46

39

73

48

73

74

60

78

Was the course useful? Consider these 12 participants as a sample from a population.
5. Write short notes on
a) Bernoulli Trials
b) Standard Normal distribution
c) Central Limit theorem