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
