Stats Midterm
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Authority
someone says it's true

Rationalism
use of reasoning to arrive at knowledge (syllogisms)

Intuition
Sudden insights

Sample
group of participants selected for study

Population
the targeted audience of your research

Independent Variable
 manipulated by the experimenter
 effect of alcohol on social behavior: IV=alcohol
 sleep deprivation on academic performance: IV=sleep deprivation

Qualitative vs. Quantitative
 Qualitative involves the type of treatment
 Quantitative defined by the amount of a variable (dosage of drug)

QuasiIndependent Variable
Independent variables that are predeterminedmaking it impossible to randomly assign subjects

Dependent Variable
measured (measure of performance)

Reliability vs. Validity
 Reliability consistency
 Validity are you testing what you say you're testing

Descriptive vs. Inferential Statistics
 Descriptive analysis done for purpose of describing or characterizing data (mean, mode, SD, variance)
 Inferential using data for sample to make inferences or draw conclusions about the population

Internal vs. External Validity
 Internal degree to which the researcher can infer that a relationship between the IV and DV is causal
 External addresses the question of generalizability

Assumptions of Statistical Tests
 1. Normality (normal distribution)
 2. Homogeneity of Variances (variability between scores is roughly equivalent)
 3. Independence of Errors (how the test is administered)

Nominal
 qualitative variables, names
 objects are measured by determining the category to which they belong
 Can compare modes but no means or medians
 Social security number, sex of a child, religion of an individual

Ordinal
 Ranking, or magnitude (1st, 2nd, 3rd..)
 No equal intervals or absolute zero
 Ratings of a task (easy, mildly difficult, difficult), marathon runners

Interval
 Magnitude and equal intervals between units, no absolute zero
 Celsius/Fahrenheit Scales

Ratio
 Magnitude, equal intervals, AND absolute zero
 Allows for all types of numerical operations
 time required to complete a task, processing speed, length, weight

Continuous vs. Discrete Variables
 Continuous infinite number of values between adjacent units on a scale (weight, height, processing speed)
 Discreteno possible values between adjacent units on a scale, it changes in fixed amounts (number of professors, cups of coffee)


Case Control
studies that begin after individuals have already developed or failed to develop the condition being investigated

Cohort
group of individuals who share a common experience

Randomized Clinical Trial (RCT)
 individuals assigned to study and control group
 "chance" (randomization) is used to assign to groups

Kurtosis
peakedness of a distribution

3 Types of Kurtosis
 1. Mesokurtic (normal)
 2. Leptokurtic (peaked)
 3. Platykurtic (flattened)

Variance
 standard deviation squared
 the higher, the more dispersed the data is around the mean
 SS/N

Standard Deviation
 how scores are dispersed around the mean
 square root of SS/N

Skewness
 symmetricality of a distribution
 can be positive or negative

Z Scores
 provides information about the location of scores in standard deviation units
 provides: direction and magnitude
 Mean= 0, SD=1

Central Limit Theorem
When the population distribution is not normal, the sampling distribution of the mean will be closer to the normal distribution than the population distribution

Comparing one group of subjects to a population
One Sample Hypothesis Testing

If a score falls within the Critical Region:
it is very unlikely to be just by chance

Random Error
 95% of the population (in the middle of the distribution)
 if Z score falls within 1.96 and +1.96, it is not statistically significant

Critical Regions
 5% of population outside of Random Error
 2.5% on each side
 if Z score falls in critical region, it is statistically significant

Hypothesis Testing is
ruling out chance

Null Hypothesis assumes:
 that there will be no statistical significance
 Goal is to disprove/reject the Null

Type I Error
Saying something is significant when it's not (false positive)

Type II Error
Saying something isn't significant, when it is (fall negative)

OneTailed vs. TwoTailed
 OneTailed: saying there is going to be a direction (this drug will increase attention)
 TwoTailed: saying it's going to be different (there is a difference in IQ between men and women)

I Have A Crazy Teacher Dave stands for:
 Hypothesis
 Alpha Level (.05)
 Critical Region
 Test Statistic
 Decision

Independent/Between Measures tTest
 Two independent group one dependent group
 Men vs. Women on time spent studying
 Exercise/Don't exercise on how many hours they sleep
 Study/Don't study on test scores

Levene's Test
 looks at if the variance between two groups is significantly different
 If it is below .05, they are significantly different (violation of your assumption)

A very difficult test will likely result in what type of skewed distribution?
negative

A sample's variability will be larger or smaller than the population from which it comes?
Smaller

The probability of Tye I Error is known as
Alpha

A Z Score has a mean of ____ and a standard deviation of _____.
 mean=0
 standard deviation=1

If raw scores from a positively skewed distribution were transformed into zscores, what shape would the standardized scores assume?
Positive

When one analyzes data based on a sample, one calculates a _____________.
Statistic

Mathematical methods used to draw tentative conclusions about a
population based on sample data are referred to as _______ statistics.
Inferential

Which study can one most reasonably determine cause and effect?
Experiment

In Inferential Statistics, the object is to generalize from a _____________ to a ______________.

Which type of measurement: Sex of a Child
Nominal

Which type of measurement: Religion of an individual
Nominal

Which type of measurement: Time required to complete a task
Ratio

Which type of measurement: Ratings of a task (Easy, Mildly Difficult, Difficult)
Ordinal

In a normal curve, the mean will be ______________ the median and mode.
Equal to

In a normal distribution, approximately ________% of the scores fall
from one standard deviation below to one standard deviation above the
mean.
68%

The attitude of one group of employees differs from attitudes of the general populationwhat is the most appropriate hypothesis test?
OneSample tTest

If Levene's test is significant, the difference in means between the two groups _____________.
Cannot be determined