Correlations range from  to , with  representing a perfect negative correlation and  representing a perfect positive correlation.

Statistically speaking, a correlation value of  indicates that if one variable is increasing, then the other variable is decreasing. Similarly, if one variable is likely to be present, then the other variable is unlikely to be present. There is a negative correlation between wearing a seatbelt and injury during a car accident.

Statistically speaking, a correlation value of  indicates that if one variable is increasing, then the other variable is also increasing. Similarly, if one variable is likely to be present, then the other variable is also likely to be present. There is a positive correlation between obesity and type II diabetes.

Statistically speaking, a correlation value of  indicates no relationship between the two variables.

Of the given answer choices, a correlation value of  gives the strongest evidence of correlation between the variables, even if the correlation is negative.

In an experiment, the independent variable is the predicted cause while the dependent variable is the predicted effect. The independent variable can be manipulated by experimentors to elicit a change in the dependent variable. The dependent variable cannot be directly manipulated.

For example, in a experiment that studies the effect of soda consumption on AP exam scores, the independent variable would be the amount of soda the subject drink (easily controlled by the experimentors) and the dependent variable would be AP exam scores (the unpredictable variable being tested).

Brenda is experiencing the placebo effect, in that she is reporting a positive effect (more energy) when she was given a blank pill. Brenda mentally prepared herself for the expected effects of the pill, and was thus able to mimic the expected outcome despite no actual biological change.

Mean is not a measure of variability - it is a measure of central tendency, along with mode and median. Measures of variability show the spread of a data set and describe how different points are from one another, whereas measures of central tendency are representative of the data set as a whole.

The Hawthorne effect is also known as "the observer effect." Subjects of a study will alter their behavior if they are aware they are being observed. Because the researcher was watching the experiment, it is possible that the subject behaved differently than he would have if he was not being watched.

Jessica's z-score indicates how many standard deviations below or above the mean Jessica's test score was. Jessica's test score of 70 was less than the mean (95), so we know that the the answer must be negative.

We know that the standard deviation was , so

Jessica's z-score is 

A PET scan measures chemical activity in the brain.

An EEG measures brain activity by detecting waves and is typically used in sleep studies.

A CAT scan uses x-rays to take images of the brain and can be useful when looking at the brain's physical structure.

An MRI also can be used to examine the structure of the brain, but uses magnetic resonance to produce images.

Introspection is when a person uses their personal experience to look inward. Wundt believed that a focused practice of introspection could be used to find and study the basic elements of the human mind. Wundt's practice of introspection fell out of favor by the 1930s, and his primary contribution to the history of science was his founding of the first experimental psychology lab, which helped formalize the study of psychology as an academic disciple.

Functionalism, while it never became a formalized school of psychological thought, had an important impact on the field. Functionalism considered thinking and behavior in terms of functional adaptation to the subject's environment. It is fallacious to say that a school of thought must have been formalized and maintained in order to have influence in a field of study.

Falsifiability is the principle that states that a research hypothesis must be able to be disproven. This does not mean that the hypothesis needs to be disproven in the study; however, hypothesis should be able to be disproven. If a hypothesis is correct under all conditions, then there is no way to scientifically test its validity.