PROBABILITY AND STATISTICS WEEK 9 Onur Doğan 2016-2017
The sampling distribution of the sample statistics Onur Doğan 2016-2017
The sampling distribution of the sample statistics Consider a population of N elements from which we can obtain the following distinct data: {0, 2, 4, 6, 8}. Form samples of size 2 for this population. Define their means and figure the bar chart of the means. Define the sampling distribution of the sample ranges and figure bar chart. Onur Doğan 2016-2017
The Central Limit Theorem The mean is the most commonly used sample statistic and thus it is very important. The central limit theorem is about the sampling distribution of sample means of random samples of size n. Let us establish what we are interested in when studying this distribution: 1) Where is the center? 2) How wide is the dispersion? 3) What are the characteristics of the distribution? The central limit theorem gives us an answer to all these questions. Onur Doğan 2016-2017
The Central Limit Theorem Let µ be the mean and σ the standard deviation of a population variable. If we consider all possible random sample of size n taken from this population, the sampling distribution of sample means will have the following properties: c) if the population is normally distributed the sampling distribution of the sample means is normal; if the population is not normally distributed, the sampling distribution of the sample means is approximately normal for samples of size 30 or more. The approximation to the normal distribution improves with samples of larger size. Onur Doğan 2016-2017
The Central Limit Theorem Onur Doğan 2016-2017
The Central Limit Theorem Onur Doğan 2016-2017
The Central Limit Theorem Onur Doğan 2016-2017
Example Consider a normal population with µ=100 and σ=25. If we choose a random sample of size n = 36, what is the probability that the mean value of this sample is between 90 and 110? In other words, what is P(90 < x < 110)? Onur Doğan 2016-2017
Example The average male drinks 2L of water when active outdoor s(with standard deviation of 0,7 L). You are planning a full day nature trip for 50 men and bring 110 L of water. What is the probability that you will run out? Onur Doğan 2016-2017