Psych 1073 Exam #1

Nominal Scale Data

Nominal Scale Data

• categorical data so it can include names, colors, labels, etc

• the order doesn’t matter. Ex, if we have red, green, and blue, one doesn’t have more value than the other

• these qualitative data can’t be used during calculation unless a number is assigned to them. Ex. 50% like red, 30% like blue and 10% like green

Ordinal Scale Data

• used to rank things. Ex. 1st, 2nd & 3rd place winners

• order matters but the distance can’t be measured because the difference in time between 1st and 2nd place can be different for 2nd and 3rd place

Interval Scale Data

• order matters and differences can be measured. Ex. 30F, 60F, 90F —> rises by + 30F

• no true zero starting point. Ex. 0 isn’t the absence of heat, there can be a negative temperature

Ratio Scale Data

• order matters and differences are measurable.

• can contain a true zero starting point. Ex. 30, 56, 70, 82, 90 grades. Differences can be measured because 56-30 is 26. 90/3 is also possible. There is also a zero point because 0 can be a grade.

• zero is the true starting point bc you can’t have a negative grade

Independent Variable

is manipulated by the researcher/experimenter

Dependent Variable

observed to assess the effect of the treatment

Properties of a Normal Distribution

• the mean, median & mode are equal

• the curve is bell-shaped and symmetric about the mean (half the scores are above the mean and half the scores are below)

• the total area under the normal curve is equal to one

• can be described by the mean and standard deviation

Properties of a Skewed Distribution

• not symmetrical

• has a tail that extends to the right or left

• in positive

  • the mean is larger than the median

  • the scores pile up on the left

• in negative

  • the mean is less than the median

  • the scores pile up on the right

What percentage of distribution is in the tails?

%5

Random sample

• the same chance of being selected

• the chance of selection doesn’t change (constant probability)

• each individual must have an equal chance of being selected

What z-scores are associated with extreme values?

+1.96 and -1.96

What proportion of scores fall between the Mean and Standard Deviation?

68% (0-1) of the data fall within one standard deviation of the mean

Law of Large Numbers

the larger the sample size (n), the more probable it is that the sample mean will be close to the population mean

Parameter

a numerical value that describes a population

Statistic

a numerical value that describes a sample

Descriptive Statistics

statistical procedures used to summarize, organize, and simplify data

Sampling Error

naturally occuring discrepancy, or error, that exists between a sample statistic and the corresponding population parameter

Discrete Variable

separate, indivisible categories; no values exist between two neighboring categories

Degrees of Freedom

the value “n-1” that’s used to calculate sample variance, so the sample provides an unbiased estimate of the population variance

Histograms

• for interval and ratio data

• the height of the bar shows the frequency for that category

• used for continuous data and group frequency