Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples Simple Random Sampling Lecture 7 Section 2 5 Robb T Koether On the TI 83 Setting the Seed Assignment Hampden Sydney College Mon Jan 26 2009 Outline Simple Random Sampling Robb T Koether 1 Homework Review Homework Review 2 Introduction Simple Random Samples 3 Simple Random Samples Selecting Samples 4 Selecting Samples On the TI 83 Setting the Seed 5 Assignment Introduction On the TI 83 Setting the Seed Assignment Homework Review Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Exercise 9 p 98 In a recent poll 62 responded Yes when asked if they favored an amendment protecting the life of an unborn child However when asked whether they favored an amendment prohibiting abortions 39 said Yes What type of bias is being observed Homework Review Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Solution The respondents are giving their answer based on their perception of the question When the question refers to protecting life they are in favor of that so they are more likely to say Yes When the question refers to prohibiting abortion they are opposed that so they are less likely to say Yes Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Recall that randomness in a large sample ensures representativeness within a very small sampling error That is because the vast majority of possible samples are representative If we pick a sample at random we are bound to get one that is representative Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Recall that randomness in a large sample ensures representativeness within a very small sampling error That is because the vast majority of possible samples are representative If we pick a sample at random we are bound to get one that is representative Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Recall that randomness in a large sample ensures representativeness within a very small sampling error That is because the vast majority of possible samples are representative If we pick a sample at random we are bound to get one that is representative Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment How could I use a coin to select a random sample of 3 students from this class By this method do all individuals have equal chances Do all samples have equal chances How could I accomplish the same using a die Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment How could I use a coin to select a random sample of 3 students from this class By this method do all individuals have equal chances Do all samples have equal chances How could I accomplish the same using a die Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment How could I use a coin to select a random sample of 3 students from this class By this method do all individuals have equal chances Do all samples have equal chances How could I accomplish the same using a die Introduction Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment How could I use a coin to select a random sample of 3 students from this class By this method do all individuals have equal chances Do all samples have equal chances How could I accomplish the same using a die Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Definition Simple random sample A simple random sample of size n is a random sample that is selected in such a way that all samples of size n have the same chance of being selected Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment A consequence of this is that all individuals in the population have the same chance of being selected for the sample Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Example Simple Random Sample A B C A B D A B E A B F A C D A C E A C F A D E A D F A E F B C D B C E B C F B D E B D F B E F C D E C D F C E F D E F For example let the population be Anthony Benjamin Christopher Destiny Emily Faith Choose one of the above samples at random What is each person s chance of being in the sample Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment However that does not work the other way around Just because a sampling method guarantees that all individuals in the population have the same chance of being in the sample it does not mean that the sample is a simple random sample Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Example Simple Random Sample Toss a coin to choose one of the following samples What is each person s chance of being in the sample A B C D E F Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83 Setting the Seed Assignment Our method will be to select individuals one at a time with all individuals equally likely at each step By this method all samples are equally likely Thus our sample will be a simple random sample Selecting a Simple Random Sample Simple Random Sampling Robb T Koether Homework Review Introduction Simple Random Samples Selecting Samples On the TI 83
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