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27 Cards in this Set
- Front
- Back
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What is descriptive statistics?
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A) Descriptive statistics refers to procedures for organizing, summarizing, and describing the data.
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What is Variability?
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A) Refers to the fact that the scores or measurement values are different from one another, even when subjects are assessed under the same circumstances.
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Why does Variability exist? Can you list 3 reasons?
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A1) The units that scientists study are rarely identical (units can include humans); Individual differences.
A2) Not everything scientists study can be measured accurately; Measurement Errors. Errors typically favor some people over others. A3) A single unit or person will not react the same way each time tested. This is called Unreliability. |
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What is statistics
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A) Statistics is the study of methods for describing and interpreting quantitative information called data.
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What is Inferential Statistics?
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A) Includes methods for making inferences about a larger group of individuals on the basis of data actually collected on a much smaller group.
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Q1) What is the difference between a population and a sample?
Q2) What is a placebo? |
A1) A population is the total number of members of a group, while, a sample is a selection individuals of the population.
A2) Placebo is a fake substance that has actually no effect on participants. |
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Scales of measurement:
1Q) What is Measurement? 2Q) What is a Scale of Measurement? |
A1) Measurement is the orderly assignment of a numberical value to a characteristic.
A2) A scale of measurement is the ordered set of POSSIBLE numbers that may be obtained by the measurement process. |
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What are the Properties of Scales?
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1) Rank order: Assigning a number to determine order.
2) Categorization or rating: Assigning groups to determine characteristics or order. 3) Magnitude: is a scale that only tells us greater than, less than, or equal to of a property/attribute. 4) Equal Intervals: When a scale has equal intervals, the magnitude of the attribute represented by a unit of measurement is the same regardless of where on the scale the unit falls. 5) Absolute Zero: Is a value which indicates nothing at all of the attribute is bring measured exists. Rank order of height does not possess absolute zero. |
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What are the properties of a Ratio Scale?
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1) Possess magnitude, equal intervals, and an absolute zero (which is necessary to make ratio statements).
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What are the properties of a Interval Scale?
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1) An interval scale has magnitude and equal intervals, but no absolute zero point. A good example of this is Fahrenheit.
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What are the properties of an Ordinal Scale?
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1) An ordinal scale only possesses magnitude, not equal intervals and absolute zero.
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What scale has none of the properties that ordinal, ratio, and interval scales have?
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1) A Nominal scale, it only categorizes mutually exclusive attributes.
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What is the difference between a Constant and a Variable?
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1) A Constant is a value that does not change. A Variable is a characteristic being measured which may take different values. Variables can include 2 nominal categories such as gender.
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What are the definitions of both Discrete and Continuos Variables?
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1A) Discrete variables are ones that have only a countable number between two points. A family can have 1, 2, 4, or 5 children (not 3.412 children).
1B) Continuos variables can have a infitnite number of variables inbetween any two points (i.e. 100.3435 lbs). |
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Describe more about real limits.
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Real limits are theoretical values that can be rounded off. Lower limits are the lowest possible half-measurement of a number. The Upper limit is the higher half measurement of above a number.
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What are the properties of the Summation symbol?
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1) The sum of a constant times a variable equals the constant times the sum of the variable.
2) The sum of a constant taken N times is N times that constant. 3) The summation of a two variables added together is the sum of one variable plus the the other variable's sum. Sigma (X + Y) = Sigma (X) + Sigma (Y). 4) To Differentiate: (Simga X)^2 means take the sum then square the total summation. Where as, Sigma (X^2) means square the values then add each of the new values up. 5) Cross Products: Sigma (XY) means to multiply the scores then add the new cross products together. |
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What is a Frequency Distribution?
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1) The Frequency Distribution indicates the number of cases observed at each score value or within each interval. The FD helps to summarize the data, save time, and convey the data's meaning. The FD is useful when we have a wide range of scores.
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What is a Relative Frequency Distribution?
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10 The RFD indicates the proportion of the total number of cases observed at each score value or interval. An advantage of this is that it expresses the pattern of scores in a manner that does not depend of a specific number of cases involved. In order to get this we need to take the frequency and divide it by N (total number of scores within the distribution). The summation of all the Rf scores should add to one!
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What is the difference between the cumulative frequency and the cumulative relative frequency?
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1) The CumF is the is the sum of the frequencies plus any score values that fall below it (typically the total N minus all scores above the desired score value).
2) CumRF is when we add the relative frequency to all the relative frequencies that fall below that score. |
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How to determine the minimum size of a class interval?
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1) Divide the range of the score values by the maximum numbers of intervals and round up.
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What is Central Tendency?
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1) A point on the scale corresponding to a typical, representative, or central score.
On a graph, central tendency is the line that dissects the graph into two. Graphs differencing in CT are identical but shifted over. |
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What is Variability?
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1) How far scores deviate from their central tendency (usually shown by the height of the graph).
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What is Skewness?
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1) Skewness refers to how asymmetrical a distribution is. The more skewness, the greater the variability. When the tail of a distribution is pulled from the right side, it is positively skewed.
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What is Kurtosis?
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Kurtosis is the curvedness of the graph. Leptokurtic (Lepto-thin) is a narrower curve while platykurtic is more flat.
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Why is Variance & Standard Deviation are more effective indicators of the variance (or how spread out the numbers are in a distribution)?
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1) Variability is a better indicator than the range because the range can include score that deviate greatly from the central tendency, but are not representative of the majority of scores. In other words, an outlier can sway range easily.
The Variance is the LEAST distanced sum of squared deviations about the mean. The Least Squares Sense: The mean is closer in terms of squared deviations to the score. Values for S^2 and S are always positive and they are (sensitive) approximations to the mean. If a value is departed from the mean, the variance will increase. It is also proportional to the average squared deviation between each & every score. When there is no variability, both SD and Variance are zero. |
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Finding the median:
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1) When N is an even number we do (N+1)/(2).
2) When N is an odd number we do (N)/2. |
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Population:
Sample: |
Parameter
Statistic |
