Types of variable, collecting data and estimation
Tell qualitative from quantitative and discrete from continuous variables, take a stratified sample, find the fair questionnaire question and تقدير a population mean from a sample.
- فلسطين: الصف ١١
- إيران: الصف ١١
- روسيا: الصف ١١
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الدليل
A متحول is a feature that differs from person to person. If its values are qualities (blood group, eye colour) it is qualitative. If they are numbers it is quantitative: discrete when we count (siblings), continuous when we measure (height, weight).
There are four ways to collect data: observation, questionnaire, interview and records. When we cannot ask the whole المجتمع الإحصائي we take a العينة: simple random, stratified (each group in proportion to its size), cluster (some whole groups) or systematic (every k-th name on a list).
A number describing the population is a parameter; a number from the sample is a statistic. The sample mean is an تقدير of the population mean; every sample gives a slightly different value and a larger sample usually has a smaller error. An interval estimate says the parameter lies between two numbers, with a stated confidence.