What is a 95 percent confidence interval? | most common statistical standard |

What is a census? | Researchers who enjoy complete access to their populations of interest are working with a census (as opposed to a sample). |

What is the central limit theorem? | For random sampling with a large sample size n, the sampling distribution of the sample mean y is approximately a normal distribution. This holds no matter what the shape of the population distribution. The result also applies to proportions. |

What are degrees of freedom? | the number of independent observations used to calculate a statistic |

What are inferential statistics? | Provide predictions about a population, based on data from a sample of that population. |

What are the mean and standard error of y? | Consider a random sample of size n from a population having mean μ and standard error σ. The sampling distribution of y gives the probabilities for the possible values of y. It has mean μ and standard error σ_{y} = σ/sqrt(n). |

What is the mean of a probability distribution? | The expected value of a realization of the distribution, E(y). For a discrete variable, the mean, μ = ΣyP(y). |

What is the normal distribution? | a distribution defined by a mathematical formula and the graph of which has a symmetrical, bell shape; in which the mean, mode, and median coincide; and in which a fixed proportion of observations lies between the mean and any distance from the mean measured in terms of the standard deviation |

What is the normal distribution? | A symmetric, bell shaped distribution characterized by its mean, μ, and standard deviation, σ. The probability within any particular number of standard deviations of μ is the same for all normal distributions. This probability equals 0.68 within 1 standard deviation, .095 within 2 standard deviations, and 0.997 within 3 standard deviations. |

What is a population? | all the cases or observations covered by a hypothesis; all the units of analysis to which a hypothesis applies |

What is a population parameter? | the incidence of a characteristic or an attribute in a population (not a sample) |

What is probability? | With a random sample or randomized experiment, the probability an observation has a particular outcome is the proportion of times that outcome would occur in a very long sequence of observations. |

What is a random sample? | A set of observations randomly drawn from the population of interest. Random selection ensures the sample is representative of the population of interest. |

What is random sampling error? | extent to which a sample statistic differs BY CHANCE from a population parameter |

What is random selection? | Random selection occurs when every member of the population has an equal chance of being included in the sample. |

Define range. | the distance between the highest and lowest values or the range of categories into which observations fall |

What is response bias? | Response bias occurs when the subject gives an incorrect response (perhaps lying), or the question wording or the way the researcher asks a question is confusing or misleading. |

What is a sample? | a subset of observations or cases drawn from a specified population |

What is a sample proportion? | the number of cases falling into one category of the variable divided by the number of cases in the sample |

What is a sample statistic? | the estimator of a population characteristic or attribute that is calculated from sample data |

What is a sampling distribution? | The probability distribution that specifies probabilities for the possible values the statistic can take. |

What is a sampling frame? | The population from which a sample is drawn. Ideally it is the same as the total population of interest to a study. |

What is selection bias? | Selection bias occurs when non-random processes - often unknown to the researcher - cause differences between test (treatment) group and the control group. |

What is a standard deviation? | A measure of dispersion of data points about the mean for interval- and ratio-level data. Standard deviation is equal to the square root of variance, and describes a typical distance from the mean. |

What is a standard error? | The standard deviation of the sample distribution of y is called the standard error of y. The standard error of y is denoted by σ_{y}. |

What is a standard error? | The standard deviation of the sample distribution of y is called the standard error of y. The standard error of y is denoted by σ_{y}. |

What is the standard normal distribution? | The normal distribution with mean μ = 0 and standard deviation σ = 1. |

What is standardization? | occurs when the numbers in a distribution are transformed into standard units of deviation from the mean of the distribution |

What is the Student's t-distribution? | a probability distribution that can be used to make inferences about a population mean when the sample size is small |

What is variance? | A measure of dispersion of data points about the mean for interval- and ratio-level data. Variance averages the squared deviations about the mean. |

What is a Z score? | the number of standard deviations by which a score deviates from the mean score |

What is cumulative density (of a distribution)? | Equals the proportion (or percentage) of the area under the curve less than a given Z score. |

What is the empirical rule? | What a normal distribution follows, where researchers can know example how often a normally distributed variable falls within one, two, and three standard errors of its mean: 68, 95, and 99% respectively. |