Week 2 - STAT 218 Week 2 Chapters 3, 4 Questions from...

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STAT 218 Week 2 Chapters 3, 4 Questions from homework or previous class? CHAPTER 3 WE WILL SKIP SECTION 3.9 SAMPLING SIMPLE RANDOM SAMPLE A sample of size n from a population of size N is a simple random sample if it was selected in such way that each of the possible observations are equally likely o Every member of the population has equal chance of being picked o The members of the sample are chosen independent of one another A random sample is supposed to resemble the population But it doesn’t always resemble the population exactly o Chance error due to sampling We do not want SAMPLING BIAS - a systemic tendency to collect some values of the population more often than we should Example – Picking Students in this class Numbers in a hat – One number for each student Other Methods for selecting a simple random sample 10 sided dice Table of random digits – Table 1 o Find random numbers between 0 and 9, or 1 and 10 o Find Random number between 10 and 99, or between 1 and 100 o Find Random number between 1 and 1000 Excel Rand Function Example Use Table 1 to pick random numbers between 1 and 40 INTRO TO PROBABILITY Probability 1
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Important to understand the main concept in order to understand statistics A probability is a numerical quantity that expresses the likelihood of an event. Grossly speaking, it is defined as the (number of favorable outcomes divided by the total number of possible outcomes) o With coins, Prob(Head) = ½ o With dice, Prob “4” = 1/6 When probability is low, it is unlikely something will happen o E.g: Winning the lottery When probability is high, it is likely to happen o E.g: It will be sunny tomorrow More Examples o Cards: P (Ace of Spades), P (a Jack) o Coin Flip: Toss three Nickels P (3 heads) ???? o Dice: P(2,3,4, or 5), o Cards: P (Heart greater than 9) o Other: Prob. of rain tomorrow Basic Concepts PROBABILITY – a numerical quantity that expresses the likelihood of an event Notation: P (E), PROB (E) A Chance operation – either the event occurs or not Probability Rules o Always a number between 0.0 and 1.0 o The sum of possible outcomes must equal 1.0. o
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This note was uploaded on 05/07/2008 for the course STAT 218 taught by Professor Staff during the Spring '08 term at Cal Poly.

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Week 2 - STAT 218 Week 2 Chapters 3, 4 Questions from...

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