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57 Cards in this Set
- Front
- Back
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What is statistics?
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It is a discipline in which mathematics and probability are applied in ways that allow researchers to make sense of their data
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What is a frequency distribution?
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It is a tally of the number of times each score is represented in a data set
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What are the 4 ways of presenting a frequency distribution?
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1. Frequency histogram
2. Grouped frequency distribution with percentages 3. Frequency distribution with percentages 4. Stem-and-leaf plot |
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How do you find cumulative frequency?
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It is formed by adding the relative frequencies of the scores up to and including the score of interest
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How do you calculate the adjusted frequency?
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by dividing the number of observations for each score by the number of valid scores for each variable, rather than by the number of participants
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What is a grouped frequency distribution?
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It is when scores are grouped together
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What is a disadvantage of the grouped frequency distribution?
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Information may be lost
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What does a histogram present?
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It presents each grouped frequency as a bar on a graph. The height of each bar represents the frequency of observations in the group
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What does the stem-and-leaf plot do?
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It presents data concisely, without losing information in the grouping process
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Researchers who often wish to collapse a set of data into a single score that represents the whole set is what?
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A central tendency
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What are descriptive statistics?
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The measures of central tendency along with the measures of variability that will follow.
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What are the three commonly used measures of central tendency?
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Mean
Median Mode |
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If a distribution is perfectly symmetric what will happen?
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The mean, median and mode will all be identical
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What is the mean?
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The arithmetic mean of a data set is the sum of the observations divided by the number of observations
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What can distort the mean?
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Extreme numbers
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What is the median?
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It is the middle score of the distribution or the score which is half of the distribution
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How do you calculate the median?
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You must first rank the score and the middle number is it
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When the number of scores is even, how do you calculate the median?
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You find the mean of the two digits
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What is the mode?
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It is the score that occurs the most
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If there are two modes then what is said of the data?
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That it is bimodal
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What is the variability of the data set?
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It is the amount of spread in the data
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What are the three measures of variability?
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Range, variance, and standard deviation
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What is the range?
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It is the difference between the highest and the lowest values in the distribution
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What is the variance?
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It is a measure of variability that, like the mean, requires that every score in the distribution be used in its calculation.
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What does the deviation score indicate?
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How high or how low a raw score is compared with the mean
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How do you generate a non-zero index of the variability within a data set?
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We must square the deviation scores. We then calculate the population variance by determining the mean of the squared deviations
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What is the symbol for the sample variance?
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It is s^2
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What is the rationale for dividing the sume of the squared deviations by N-1?
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It rests on the concept of degrees of freedom
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How can degrees of freedom be understood?
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Ex: in a sample of 10 values with a known mean, nine of the values are "free" to fluctuate, as long as the investigator has control over the final value
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For the mean, there are always what?
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N-1 degrees of freedom
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Why in world do you need to use degrees of freedom?
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Using the degrees of freedom for the mean as the denominator of the sample variance formula leads to an unbiased estimation of the population variance
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What is the population variance?
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It is the mean of the squared deviations from the mean
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What is the sample variance?
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It is the sum of the squared deviations from the mean, divided by the degrees of freedom for the mean
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How do you calculate the standard deviation?
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It is the square root of the variance and is expressed in the units of the original measure
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What is the population standard deviation?
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it is the squared of the population variance
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What is the sample standard deviation?
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It is the square root of the sample variance
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What is the notation for the variance?
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The square of the notation for standard deviation
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Taken together, the measures of central tendency and variability are referred as what?
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descriptive measures
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When descriptive measures are used to describe a population what are they known as?
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Parameters
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When descriptive measures are used to describe a sample, what are they known as?
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Statistics
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Groups of measurement that frequently approximate a bell-shaped distribution are known as what?
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A normal curve
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The normal curve is what?
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Is a symmetric frequency distribution that can be defined in terms of the mean and standard deviation
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What is a z-score?
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It is a score that can be expressed in terms of how many standard deviations it is above or below the mean
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How is a z-score calculated?
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It is calculated by dividing the deviation score by the standard deviation
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What is the standard normal distribution?
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Is when a normally distributed set of data is converted to z scores, the distribution of the z score is known as the standard normal distribution
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What is the sampling distribution?
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It is a specific type of normal distribution
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What is a sampling distribution?
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The distribution of the means of several samples
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What is the SEM (standard error of the mean?)
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It is the standard deviation of the sampling distribution
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What does the SEM (standard error of the mean) vary with?
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With the sample size
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How do you find the Standard error of the mean?
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It is found by dividing the sample standard deviation by the square root of the number in the sample
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What are inferential statistics?
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The branch of statistics that is used to determine whether, among other things, there are significant differences between groups
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What is a null hypothesis?
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It is the statistical hypothesis being tested that has the hypothesis of no statistically significant difference
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If the probability of the Null Hypothesis is low then what?
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We conclude that the null hypothesis is false
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If the probability of the Null Hypothesis is high then what?
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we conclude that Null Hypothesis is true
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What is the alpha level inflation?
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This occures when researchers conduct many statistical tests within a given study
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What is the Alpha level?
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It is the conventional level of chance that is tolerated which is 5% or .05 it is the lowest level of inconsistency that the researcher is willing to tolerant to make the study significant
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What is the power of a test?
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It is the likelihood that it will detect a difference when one exists.
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