# Shared Flashcard Set

## Details

Research and Design Test 2
na
58
Psychology
02/02/2013

Term
 Definitional Formula for Sum of Squares
Definition
 SS = Sigma(X - mu)^2 Best to use if you have a small group of scores and the mean is a whole number.
Term
 Three Steps of finding Sum of Squares - Definitional
Definition
 1. Find each deviation score (X - mu)2. Square each deviation score (X - mu)^23. Add the squared deviations.
Term
 Computation Formula for Sum of Squares (population)
Definition
 SS = SigmaX^2 - [(SigmaX)^2]/NUse most of the time.
Term
 Three Steps of finding Sum of Squares - Computational (population)
Definition
 1. Square each score and then add the squared values. SigmaX^22. Find the sum of scores, then square this total and divide the results by N.3. Subtract the second part from the first.
Term
 Population Variation Equation
Definition
 variance = SS/N
Term
 Population Standard Deviation Equation
Definition
 standard deviation = Square Root of: (SS/N)
Term
 Three Steps to finding Sum of Squares for a Sample
Definition
 1. Find the deviation for reach score: deviation = X - M2. Square each deviation: squared deviation = (X - M)^23. Add the squared deviations: SS = Sigma(X - M)^2
Term
 Definitional Formula for Sum of Squares for Sample
Definition
 SS = Sigma(X - M)^2
Term
 Computational Formula for Sum of Squares for Sample
Definition
 SS = SigmaX^2 - [(SigmaX)^2/n]
Term
 Sample Variance Formula
Definition
 s^2 = SS/(n-1)
Term
 Sample Standard Deviation Formula
Definition
 s = Square Root of s^2 = Square Root of SS/(n - 1)
Term
 Degrees of Freedom Formula
Definition
 df = n = 1
Term
 Error Variance
Definition
 The sample variance represented unexplained and uncontrolled differences between scores. (In the context of inferential statistics).
Term
 Variability
Definition
 Measure the extent to which our observations are spread out or clustered together.
Term
 Range
Definition
 A type of variability, difference between highest and lowest value.
Term
 Interquartile Range (IQR)
Definition
 A type of variability, range of middle 50% (chop off top and bottom 25%)
Term
 How to find IQR
Definition
 1. Find overall median2. Throw it away3. Find median for upper/lower half4. Subtract
Term
 Variance
Definition
 A form of variability, measures, on average how far away are our observations from the mean? What is the average deviation?
Term
 z-score
Definition
 Specifies the precise location of each X value within a distribution. (+ or -) signifies whether the score is above the mean (positive) or below the mean (negative).
Term
 Standard Distribution
Definition
 Composed of scores that have been transformed to create predetermined values for mu and sigma (o). Used to make dissimilar distributions comparable.
Term
 Probability
Definition
 Defined as a fraction or a proportion of all possible outcomes for a situation in which several different outcomes are possible.
Term
 Formula for Probability
Definition
 If the possible outcomes are identified as A, B, C, and D then:Probability of A = (number of outcomes classified as A)/(total number of possible outcomes)
Term
 Random Sample
Definition
 Requires that each individual in the population has an equal chance of being selected. A second requirement, necessary for many statistic formulas, states that the probabilities must stay constant from one selection to the next if more than one individual is selected.
Term
 Sampling Error
Definition
 The natural discrepancy, or amount of error, between a sample statistic and its corresponding population parameter.
Term
 Distribution of Sample Means
Definition
 Collection of sample means for all the possible random samples of a particular size (n) that can be obtained from a population.
Term
 Sampling Distribution
Definition
 A distribution of statistics obtained by selecting all of the possible samples of a specific size from a population.
Term
 Expected Value of M
Definition
 The mean of a distribution of sample means is equal to the mean of population scores, and mu.
Term
 Standard Error of M
Definition
 Standard error provides a measure of how much distance is expected on average between a sample mean (M) and the population mean (mu)
Term
 Law of Large Numbers
Definition
 States that the larger the sample size (n), the more probable it is that the sample mean will be close to the population mean.
Term
 Hypothesis Test
Definition
 A statistical method that uses sample data to evaluate a hypothesis about a population.
Term
 Null Hypothesis
Definition
 States that in the general population there is no change, no difference, or no relationship. In context of an experiment, this predicts that the independent variable has no effect on the dependent variable for the population.
Term
 Alternative Hypothesis
Definition
 States that there is a change, a difference or a relationship for the general population. In the context of an experiment, this predicts that the independent variable does have an effect on the dependent variable.
Term
 Alpha Level / Level of Significance
Definition
 A probability value that is used to define the concept of "very unlikely" in a hypothesis test.
Term
 Critical Region
Definition
 Composed of the extreme sample values that are very unlikely (as defined by the alpha level) to be obtained if the null hypothesis is true. The boundaries for this are determined by the alpha level. If sample data fall here, the null hypothesis is rejected.
Term
 Type I Error
Definition
 Occurs when a researcher rejects a null hypothesis that is actually true. This means the researcher concludes that a treatment does have an effect when it in fact has no effect.
Term
 Type II Error
Definition
 Occurs when a researcher fails to reject a null hypothesis that is really false. In a typical research situation, this means that the hypothesis test has failed to detect a real treatment effect.
Term
 Significant / Statistically Significant
Definition
 A result is said to be this if it is very unlikely to occur when the null hypothesis is true. That is, the result is sufficient to reject the null hypothesis. Thus, a treatment has a significant effect if the decision from the hypothesis test is to reject the null hypothesis.
Term
 Directional Hypothesis Test / One-Tailed Test
Definition
 The statistical hypotheses specify either an increase or a decrease in the population mean. That is, they make a statement about the direction of the effect.
Term
 Effect Size
Definition
 The measure of this is intended to provide a measurement of the absolute magnitude of a treatment effect, independent of the size of the samples being used.
Term
 Power
Definition
 The probability that the test will correctly reject a false null hypothesis. That is, this is the probability that the test will identify a treatment effect if one really exists.
Term
 Raw Scores
Definition
 Original, unchanged scores that are the direct result of measurement.
Term
 1. Each z-score tells the exact location of the original X value within the distribution.2. The z-scores form a standardized distribution that can be directly compared to other distributions that also have been transformed into z-scores.
Definition
 Two useful purposes of transforming X values into z-scores.
Term
 Deviation Score
Definition
 The distance in points between X and mu and indicates whether X is located above or below the mean.
Term
 Shape of a z-score
Definition
 Will be the same as the original distribution of raw scores.
Term
 Mean of a z-score
Definition
 The z-score distribution will always have a mean of zero.
Term
 Standard Deviation of a z-score
Definition
 The distribution of z-scores will always have a standard deviation of 1.
Term
 Relabeling
Definition
 z-score transformation
Term
 p
Definition
 probability
Term
 Sampling with Replacement
Definition
 The process of returning each individual to the population before you make the next selection.
Term
 Unit Normal Table
Definition
 This table lists proportions of the normal distribution for a full range of possible z-score values.
Term
 Body
Definition
 Larger section of the normal distribution separated by a vertical line.
Term
 Tail
Definition
 Smaller section of the normal distribution separated by a vertical line.
Term
 1. If you know a specific location (z-score) in a normal distribution, you can use the table to look up the corresponding proportions.2. If you know a specific proportion (or proportions), you can use the table to look up the exact z-score location in the distribution.
Definition
 Two purposes of the unit normal table.
Term
 1. Transform the X values into z-scores2. Use the unit normal table to look up the proportions corresponding to the z-score values.
Definition
 Two steps to answering probability questions about scores from a normal distribution.
Term
 Percentile Rank
Definition
 Defined as the percentage of the individuals in the distribution who have scores that are less than or equal to the specific score.
Term
 Percentile
Definition
 When a score is referred to by its percentile rank.
Term
 Central Limit Theorem
Definition
 For any population with mean mu and standard deviation sigma, the distribution of sample means for sample size n will have a mean of mu and a standard deviation of sigma divided by square root of n and will approach a normal distribution as n approaches infinity.
Term
 1. The population from which the samples are selected is a normal distribution.2. The number of scores (n) in each sample is relatively large, around 30 or more.
Definition
 How to make the distribution of sample perfectly normal.
Supporting users have an ad free experience!