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Chapter 3: Central Tendency
Chapter 4: Variability
Chapter 5: z-Scores:…
Chapter 3: Central Tendency
Chapter 4: Variability
Chapter 5: z-Scores: Location of Scores and Standardized Distributions
Central tendency: measure of statistics to determine a single score that defines the middle of a distribution Link Title
Mean: sum of all of the scores divided by the number of scores; it is referred to as the average; it can be found using a formula. If one value is changed, the mean will also change. When the data is symmetric, the best measure to use is the mean. ![Mean](attached://3f582bbf64927a9f8453ad6ed4e31da2 150x60) [Link Title](https://www.youtube.com/watch?v=0io9U8Jcjeo)
median: midpoint of a distribution of scores listed in ascending order; it can be found for an open-ended distribution; it is appropriate for ordinal data; it can be found when there are underdetermind scores. The the data has a negative or positive skewness, the median is the best measure to use.
Mode: the number that occurs the most; there can be more than one mode. ![Mode](attached://2df3cbaa255bacf72edd3b403af6f862 150x125)
- Range is the difference between the highest and the lowest scores.
Bimodal: distribution with two modes
Line graph: display in which points connected by straight lines show several different means
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Standard Deviation and Descriptive Statistics
How is the standard deviation represented in a frequency distribution graph? By a horizontal line or arrow extending from the mean for a distance equal to one standard deviation.
What symbols are used for the mean and standard deviation for a sample in a research report? The mean is identified by the letter M and the standard deviation is represented by SD.
A standard deviation of zero indicates there is no variability. In this case, all of the scores in the sample have exactly the same value.
For symmetrical distributions, the mean will equal the median. If there is only one mode, then it will have the same value, too. In a skewed distribution, the scores tend to pile up toward one end of the scale and taper off gradually at the other end.
Attached is the formula for computing the z-score. Listed in individual branches are the 4 steps involved in computing the z-score.
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Step 4: Confirm the answer using the z-score formula; also, I used the normalcdf my Texas-Instrument 84-Plus calculator to confirm my z-scores.
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The relationship between z-score values and locations in a population distribution.
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What is z-score transformation? It is the changing raw scores into z-scores; process changes raw scores into standard scores with mean 0 and standard deviation 1
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