W1L1-Intro_to_Stats233234536

# W1L1-Intro_to_Stats233234536 - Introduction to Statistics...

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Click to edit Master subtitle style Introduction to Statistics Measures of Central Tendency

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Why and when do we need statistics? To summarise our data What is the mean of our data? How much spread is there in the data? Quality assessment Is there too much spread in our data? Are our results real? What is the probability an effect happened by chance? Are our results SIGNIFICANT? ‘Can we represent our data in a better light?’
Two Types of Statistics Descriptive statistics of a POPULATION Relevant notation (Greek): w mean N population size l sum Inferential statistics of SAMPLES from a population. Assumptions are made that the sample reflects the population in an unbiased form. Roman Notation: X mean n sample size l sum

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Be careful though because you may want to use inferential statistics even when you are dealing with a whole population. Measurement error or missing data may mean that if we treated a population as complete that we may have inefficient estimates. It depends on the type of data and project. Example of Democratic Peace.
Also, be careful about the phrase “descriptive statistics”. It is used generically in place of measures of central tendency and dispersion for inferential statistics. Another name is “summary statistics”, which are univariate: Mean, Median, Mode, Range, Standard Deviation, Variance, Min, Max, etc.

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Creating Frequencies We create frequencies by sorting data by value or category and then summing the cases that fall into those values. How often do certain scores occur? This is a basic descriptive data question.
Plotting Data: describing spread of data A researcher is investigating short-term memory capacity: how many symbols remembered are recorded for 20 participants: 4, 6, 3, 7, 5, 7, 8, 4, 5,10 10, 6, 8, 9, 3, 5, 6, 4, 11, 6 We can describe our data by using a Frequency Distribution. This can be presented as a table or a graph. Always presents: The set of categories that made up the original category

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W1L1-Intro_to_Stats233234536 - Introduction to Statistics...

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