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 |
0-5 | 5-10 | 10-15 | 15-20 | 20-25 | 25-30 | 30-35 | 35-40 |

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

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