Stats easy answers 4.0 / 5 based on 2 ratings ? StatisticsEasy AnswersGCSEAQA Created by: medinap110Created on: 03-02-16 20:46 What is meant by random sample? Each item in a population has an equal chance of being chosen 1 of 17 How do you take a random sample? 1) Number all the pieces of data. 2) Random number generator. 3) Select pieces of data which correspond to the random numbers. 2 of 17 Comparing Box Plots IQR, median, and skew (but only the inside of the box, not the whiskers) 3 of 17 Sample instead of census? Quicker and cheaper 4 of 17 Write a suitable question 1) Time frame. 2) Non-overlapping boxes. 3) "Other" box 5 of 17 Why is a graph misleading? 3D or distorted? Confusing gaps? Uneven scale on axis? 6 of 17 Which distribution is it? Uniform - Each outcome has an equal chance. Binomial - mutually exclusive events. 3) Normal - naturally occurring. 7 of 17 Comparative pie charts Always about area of pie charts 8 of 17 Scatter graphs +line of best fit Extrapolation is very bad >. 9 of 17 Relationship between two variable on scatter graphs 1) Positive/negative 2) As one gets bigger/smaller the other gets bigger/smaller 10 of 17 Why use a control group? Compare the impact of change on a group that has had no change. 11 of 17 Why pilot survey? 1) Check q's are understood. 2)Relevant answers. 3) Check response rates. 4) Can change q's. 5)How long it will take. 12 of 17 Suitable sample? Equal chance of being chosen? Biased in any way? 13 of 17 What sample frame could be used? Needs to be a specific population, ie list of everyone in payroll or everyone on electrical register. 14 of 17 One advantage and one disadvantage of using a sample. Quick, cheap, less accurate, may suffer from bias. 15 of 17 Describe trends. Focus on trends, not numbers. So: Population increases in size (not: goes from 20 to 40) 16 of 17 Why take/what is a stratified sample? Proportionally represents the population. 17 of 17
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