Scientific Inquiry Exam 2

ordinal scale

Demonstrates rank by showing difference and direction of difference (but not amount) o Provide more info than nominal o We don't know the difference though (no equality of units) - 1st place was better than 2nd and so on but no measure of difference between

range

Measures the distance between the high score and the low score. Weak measure of variability because it only used 2 extreme scores

ratio scale

Most complex, with all of the elements of interval scale plus an absolute zero point (absence of a trait) Weight, distance and time all have meaningful absolute zero points Absolute zero points allows us to make comparisons - 5 inches is half of 10 inches

standard deviation

Most frequently used and stronger than range. Tells us the average algebraic distance from the mean of each score in a distribution. - A larger SD means there is more variability on scores or they are more spread out

Positively skewed curve

Most of its scores are depicted in the left, or lower value, side of the distribution with the tail pointing in the positive direction

negatively skewed curve

Most of its scores are on the high value side with the tail pointing left

Nominal Scale

Most rudimentary, providing only information about a difference (name) o Jersey #13 is different from jersey #85 o Interstate 77 is different than SR 62

Interval scale

Obtain all of the properties of ordinal measures plus equality of units. Difference, direction of difference and amount of difference (in equal units) are contained - 20 degrees is 5 degrees less than 25 May also contain a zero point (arbitrary zero) Does not reflect absence of a trait

Inferential use of statistics

Occur when one makes generalization or interferences from a smaller group to a larger group. - Prediction is made by measuring a trait from a representative group and estimating what it would be in a larger group - Ability to infer is not so much statistical, but in the purpose for using it

The normal curve

A statistical and theoretical model that is used to visualize data, to interpret distributions of scores, and most importantly, to make predictions & probability statements

Population

All-inclusive group that is operationally defined by researcher, membership is exclusive

skewed

Atypical distributions that occur when a distribution of scores will not fit the model of the normal curve and non-normal cure result

sample

a representative subset of the population that contains all of the essential elements of that population

parameter

a trait or characteristic of a population

Z score

Used to convert a raw score from a distribution into units of the normal curve called SD units. - Gives raw score distance from the mean in SD units (informs of the exact position of the raw score in a distribution) - Importance of means and standard distributions - (Raw score - mean) /std dev

nonparametric statistics

Used when data is nominal or ordinal or when the population from which the observations were made are though not to be normally distributed

Descriptive use of statistics

Used when measuring a trait or characteristic of a group without an intention to generalize that stat beyond that group

coefficent of variation

Used when the measurement means or variables of two or more distributions are not the same

parametric statistics

Used when the research data are interval or ratio and when the populations from which the observations were made are though to be normally distributed. Considered more powerful because they are more likely to reject a false hypothesis.

type 2 error

When a false null hypothesis is accepted o Beta level is the probability of making a ____ error

mean

average; most common most reliable and meaningful measure of central tendency

mode

most frequent score; most crude

null hypothesis

statement of no difference or no relationship. Assumed to be true until proved otherwise

Statistic

trait or characteristic of a sample

Type 1 error

A null hypothesis is rejected when it's actually true o When you say there is a difference but there actually is not o Alpha level is the probability of making a _____ error

Theoretical Probability

The number of ways an event can occur divided by the number of possibilities

Absolute scale

The result when the number of events or observations is made to the whole unit - Number of people in this class, on the basketball team, etc. - There are not 12.7 players on the bball team

level of significance

The statistical reference point that is selected for the purpose of accepting or rejecting the null hypotheses. Set by the researcher and defines the probability of an even occurring often vs rarely due to sampling error

alternative hypothesis

the logical state of reality that must exist if the null hypothesis is not true

median

the middle; better if has a large outlier

variance

the square of the standard deviation