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UH KIN 4310 - Variability, Standard Deviation, and Different Types of Studies
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KIN 4310 1st Edition Lecture 2 Outline of Last Lecture I Section 1 Topics II The Scientific Method III Scientific Knowledge IV Examples of Hypothesis V Examples of Hypothesis 2 VI Examples of Hypothesis 3 VII Examples of Hypothesis 4 VIII Definitions IX Types of Data X Definitions XI Definitions XII Definition XIII Types of Statistics XIV Chapter 2 XV Definition XVI Mean Arithmetic Mean XVII Notation XVIII Notation XIX Definitions XX Finding the Median XXI Definitions XXII Which Measure of Central Tendency to Use XXIII When to Use Mode XXIV When to Use Median XXV When to Use Mean Outline of Current Lecture I Excel Functions II Variability III Why Variability is Important IV Measures of Variability V Definition VI Definition VII Sample Standard Deviation Formula These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute VIII IX X XI XII XIII XIV XV XVI XVII Why n 1 Standard Deviation Important Properties Things to Remember Computing Variance Standard Deviation or Variance Excel Functions Methodological Approaches Descriptive Studies Correlation Studies Experimental Studies Current Lecture I Excel Functions a Mean i AVERAGE selection b Median i MEDIAN selection c Mode i MODE selection ii This mode function only shows the smallest mode so don t really rely on this d N i COUNT selection ii Use the SORT tool in the DATA menu to organize your data II Variability a How spread out is the data b In the chart about the presidents i There is variability between presidents ii There is variability within president iii There is variability between democrats and republicans III Why Variability is Important a Variability how different scores are from the mean i Spread ii Dispersion b So variability is really a measure of how each score in a group of scores differs from the mean of that set of scores c Can be considered the average distance from the center IV Measures of Variability a Three types of variability that examine the amount of spread or dispersion in a group of scores i Range ii Standard deviation iii Variance b Typically report the mean and the variability together to describe a distribution V Definition a The range of a set of data is the difference between the maximum value and the minimum value b Range maximum value minimum value VI Definition a The standard deviation of a set of sample values is a measure of variation of values about the mean b The most common known measure of variability VII Sample Standard Deviation Formula a b c d VIII IX s is always positive x is the number in the sample x bar is the sample mean the numerator is also called the sum of squares Why n 1 a The standard deviation is intended to be an estimate of the POPULATION standard deviation i We want it to be an unbiased estimate ii Subtracting 1 from n artificially inflates the SD making it larger 1 This makes it hard to prove things be conservative b In other words we want to be conservative in our estimate of the population Standard Deviation Important Properties a The standard deviation is a measure of variation of all values from the mean b The value of the standard deviation s can increase dramatically with the inclusion of one or more outliers data values far away from all others i Outliers have a big effect on standard deviation ii Ex a 7 ft person in our study c The units of the standard deviation s are the same as the units of the original data values X Things to Remember a Standard deviation is computed as the average distance from the mean b The larger the standard deviation the greater the variability c Like the mean standard deviation is sensitive to extreme scores d If s 0 then there is no variability among scores they must all be the same value i s 0 is possible ii it is impossible to have a SD number XI Computing Variance a Variance standard deviation squared b So what do these symbols represent XII Standard Deviance or Variance a Although the formulas are quite similar the two are also quite different i Standard deviation is stated in original units ii Variance is stated in units that are squared iii Which is easier to interpret 1 Standard deviation is Excel Functions a Range i MAX selection MIN selection b Standard deviation i STDEV selection c Variance i VAR selection XIII XIV Methodological Approaches a Descriptive X is Y i How things are ii One third of US citizens are obese iii This is observational b Correlational X is related to Y i How things are in relation to other things ii Most people who are obese also have comorbid health compromising conditions iii This is also observational c Experimental X causes Y i How things are and how they got that way ii People with an energy imbalance will gain weight and may become overweight or obese iii Not observational XV Descriptive Studies a Most common type of study he s not sure about this b Describes how it is c Observe and measure specific characteristics without attempting to modify the subjects that are being studied d Examples i Our stature study ii Life expectancy in different countries iii Prevalence of Spinal Cord Injury in males and females e What are the facts XVI Correlation Studies a Used commonly in health science studies b Describes something in relation to something else c Observations are not manipulated merely related to each other d Examples i Correlation between body fat percentage and aerobic fitness ii Correlation between commuting distance and body mass index XVII Experimental Studies a Hard to do well b Apply some treatment and then observe its effects on the subjects c Even with a strong experimental design you still may not get your answer d Used sometimes in evaluation but typically to explain descriptive evaluations e Example i The Antihypertensive Effects of Fish Oil ii 14 people with high blood pressure iii Randomized into 2 groups 1 Group A Ate fish oil diet for 4 weeks 2 Group B Ate a standard oil diet for 4 weeks iv Measurement Blood Pressure before and after the diet


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UH KIN 4310 - Variability, Standard Deviation, and Different Types of Studies

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