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# Basic research/Stat

### Chapter 6&7

Term | Definition |
---|---|

Probability | The study of the likelihood and uncertainty ; the # of ways a particular outcome can occur divided by the total # of outcomes. EX; HEADS OR TAILS 1 OUTCOME AND TWO POSSIBILITIES. |

Hypothesis testing | The PROCESS of determining whether a hypothesis is supported by the results of a research study. IT IS BUILT ON PROBABILITY. it focuses on the differences between groups or relationships observed. |

Multiplication rule | Probability rule stating that the probability of a SERIES of outcomes occurring on a successive trails is the product of their individual probabilities, when the sequence of outcomes is independent. FLIP A COIN 1 TIME YOU GET A HEAD THAN TALES .5*.5=.25 |

Addition rule | The probability of one outcome or another outcome occurring on a particular trail is the sum of their individual probabilities , when the outcomes are mutually exclusive. 1/6 getting a 6 1/6 2/6 |

Null hypothesis | Predicting that NO DIFFERENCE exists between the groups being compared. |

Alternative hypothesis | the researcher wants to support, predicting that a significant difference exists between the groups being compared |

Null for correlation | Predicts NO RELATIONSHIP |

Alternative for correlation | predicts yes that there is a relationship |

Non Directional 2 tailed Hypothesis | An alternative hypothesis in which the researcher predicts that the groups being compared ARE DIFFERENT BUT DOES NOT PREDICT THE DIRECTION OF THE DIFFERENCE. |

Directional 1 tailed hypothesis | An alternative hypothesis in which the researcher predicts the direction of the expected difference between the groups. THE COMPARISON IS THE DV. |

type 1 error | we said there was a difference when there wasn't. Null hypothesis is rejected when it is true. |

Type 2 error | we said there is not a difference when there was. Null hypothesis is not rejected when it is false. |

statistical significance | when the probability of a type 1 error is low (.05 or less) the difference between the groups is so large that we conclude it is due to something other than chance. |

single group design | a research study in which there is only one group of participants. |

Inferential statistics | procedures for drawing conclusions about a population based on data collected from a sample. |

parametric test | a statistical test that involves making assumptions about estimates of population characteristics or parameters. Z TEST AND T TEST. |

non parametric test | a statistical test that does not involve the use of any population parameters U and standard deviation are not needed and the underlying distribution does not have to be normal. |

Magnitude | an indication of the strength of the relationship between 2 variables |

scatter plot | a figure the graphically represents the relationship between 2 variables. |

TYPES OF MISINTERPRETATIONS | |

causality | the assumption that a correlation indicates a casual relationship between 2 variables. |

Directionality | The interference made with respect to the direction of a causal relationship between 2 variables |

Third variable problem | The problem of a correlation between 2 variables being dependent on another (third) variable. |

Restrictive range | A variable that is truncated (shorten) and has limited variability |

Curvilinear Relationship | the curved nature of the relationship decreases the observed correlation coefficient |

Partial correlation | a correlation technique that involves measuring 3 variables and then statistically removing the effect of the third variable from the correlation of the remaining 2 variables. |

TYPE OF RELATIONSHIP (NONE) | variables are unrelated and do not move together in any way |

TYPE OF RELATIONSHIP (Curvilinear) | Variables increase together up to a point and then, as one continues to increases the other decreases. |

Person who argument | arguing that a well established statistical trend is invalid because we know a person who went against the trend. |

Pearson product moment correlation coefficient Pearson's r | The most commonly used correlation coefficient when both variables are measured on an interval or ratio scale. |

coefficient of determination r2 | A measure of the proportion of the variance in one variable that is accounted for by another variable calculated by squaring the correlation coefficient |

Spearman's rank order correlation coefficient | the correlation coefficient used when one or more of the variables is measured on an ordinal ranking scale. |

point biserial correlation coefficient | The correlation coefficient used when one of the variables is measured on a dichotomous nominal scale and the other is measured on an interval or ratio scale. |

Phi coefficient | The correlation coefficient used when both measured variables are dichotomous and nominal. |

Regression analysis | a procedure that allows us to predict an individuals score on one variable based on knowing one or more other variables. |

Regression line | The best fitting line straight line drawn through the center of a scatter plot that indicates the relationship between the variables |

z test | A parametric inferential statistical test of the null hypothesis for a single sample where the population variance is known |

sample distribution | A distribution of sample means based on random samples of a fixed size from a population |

standard error of the mean | The standard deviation of the sampling distribution |

central limit theorem | A theorem that states that for any population with a mean u and a standard deviation q, the distribution of sample means for sample size N will have a mean of u, a SD of q/ square rootN and will approach a normal distribution as N approaches infinity |

Critical Value | The value of a test statistic that marks the edge of the region of rejection in a sampling distribution where values equal to it or beyond it falls into the region of rejection |

Region of rejection | The area of a sampling distribution that lies beyond the test statistics critical value when a score falls within this region H0 is rejected |

statistical power | The probability of correctly rejecting a false H0 |

T test | A parametric inferential statistic test of the null hypothesis for a single sample where the population variance is not known |

Students t distribution | A set of distributions that although symmetrical and bell shaped are not normally distributed |

Degrees of freedom df | The number of scores in a sample that are free to vary. |

Estimated standard error of the mean | An estimated of the standard deviation of the sampling distribution |