sampling simple random sampling

sampling simple random sampling

1. Population… Collection of all the items related to an enquiry is called population.

2. Sample … …A sample is a representative part of population

3. sampling Process of selecting sample from population is called sampling

4. The sampling process… POPULATION SAMPLE INFERENCE

5. Population Possible Samples TV’s produced by a factory.. Every 20 th TV Children’s pants made in a factory. Every 30 th pair Punctuality of buses in a city. Check punctuality for 10 different routes Tire produced by manufacturer. 5 tyres produced

6. Why do we take a Sample? whySampling? Too expensive and too time consuming to survey an entire population population

7. Simple random sampling ( Unrestricted sampling ) is process of drawing a sample from population in which each and every unit has equal chance of included in sample.and are divided to two SRS WITH REPLACEMENT AND WITHOUT REPLACEMENT

8. Simple Random Sample Every subset of a specified size n from the population has an equal chance of being selected

9. (S.R.S) without replacement If selected unit is not replaced before second draw then sampling method is called ( s.r.s ) without replacement

10. Simple random sampling with replacement After a unit has been selected by this method it may or may not replaced before second draw if replaced before next draw it is simple random sampling with replacement

11. SOME EXAMPLE For example, if we catch fish, measure them, and immediately return them to the water before continuing with the sample, this is a WR design, because we might end up catching and measuring the same fish more than once. However, if we do not return the fish to the water (e.g. if we eat the fish), this becomes a WOR design.

12. Difference of s.r.s with replacement and without replacement When we sample with replacement the two values are independent.This means first result doesnt affect second result.but when we sample without replacement the first result affect happening of second result.

13. TYPES OF S.R.S THERE ARE 2 TYPE OF METHOD OF SELECTING SIMPLE RANDOM SAMPLING 1>LOTTERY METHOD 2>RANDOM NUMBER TABLE

14. LOTTERY METHOD In this method all items in population are named or numbered serially on separate slips of paper having identical shape and size and are mixed in bowl then required number of slips are selected at random

15. Hat Simple Random Sampling 24 38 14 43 Method 1 Example : Out of a CLASS of 50 students 15 are to be selected to take part in a FEST. 1 . Assign ROLL number from 1 to 50 to each student. 2 . Write each number on a piece of paper (or use raffle tickets), place in a hat and mix up. 3 . Draw the 15numbers from the hat.

16. Random number tables Lottery method is difficult to adopt if size of population is very large.In such case random number tables are used.Of the tables pippett table is most popular one, which consists of 10400(ten thousand four hundred) sets of four digit random numbers

17. Eg:suppose we want to select a sample of size ‘15’ from a population of 5000 then number then number all 5000 item from 1to 5000.select apage at random from table and choose first 15 numbers which are less than or equal to 15.