QUESTIONS, ANSWERS & THEIR
RESPECTIVE MARKS
"What is an independent variable (IV)? - CORRECT ANSWER An IV is the influencing
factor / which a researcher manipulates in an experiment / in order to observe its effect
on a DV / for example, in a study of the effect of alcohol on driving ability, the IV would
be the amount of alcohol given to the drivers. (4 marks)"
"What is a dependent variable (DV)? - CORRECT ANSWER A DV is the factor in an
experiment which is influenced by changes in the IV / and which is observed and
measured by the researcher. / In the example given in 3, the DV would be driving ability.
(3 marks)"
"What is a confounding variable? - CORRECT ANSWER A confounding variable is an
influence in an experiment that is not the IV yet causes changes in the DV. / For
example, researchers may find age affects IQ in that older people do less well than
younger people. / However, this could be due to the confounding variable of how the
test is approached. Older people may be more careful and less concerned about
'beating the clock' than are younger people, consequently, their scores are lower. (3
marks)"
"What is an extraneous variable? - CORRECT ANSWER Extraneous variables are all
other variables apart from the IV and DV that need to be controlled in an experiment /
e.g. the testing environment, time of day, instructions to participants. / If extraneous
variables are not taken care of they could obscure the effect of the IV / or, if systematic,
turn into a confounding variable. (4 marks)"
"What is a control group? - CORRECT ANSWER In a simple two-sample experiment,
control group participants are affected by everything the experimental group
experiences with the exception of the IV. / Scores from the control group thus provide
baseline data / against which scores from the experimental group can be compared. (3
marks)"
"Distinguish between independent groups, matched pairs and repeated measures
designs - CORRECT ANSWER These are experimental designs / used to control
variation due to individual differences between participants. / In a simple experiment
comparing two conditions, the independent groups design consists of two different
groups of participants / who have been allocated by chance to either of the two
conditions. / Matched pairs designs involve pairing participants on variables relevant to
the study / then splitting the pairs and randomly allocating the members of the pair to
, one or other condition. / In a repeated measures design, participants undergo both
conditions in the experiment. (7 marks)"
"What are practice effects? - CORRECT ANSWER Practice effects occur in repeated
measures designs / when participants carry over an improvement to the second
experimental condition / as a result of having done the first condition. / (In this case,
practice becomes a confounding variable.) (4 marks)"
"How are standard errors and confidence intervals related? - CORRECT ANSWER
Standard errors can be used to calculate confidence intervals / for any given statistic. (2
marks)"
"Between which two values can a correlation coefficient vary? - CORRECT ANSWER
Correlation can vary between +1.00 and -1.00. (2 marks)"
"Is a correlation of - .8 weaker than a correlation of + .8? Explain. - CORRECT
ANSWER The two correlation values are the same strength as each other / because
the numerical value (.8) is the same. / They differ only in that they show relationships in
different directions i.e. positive and negative. (3 marks)"
"What is partial correlation? Give an example - CORRECT ANSWER Partial correlation
is when the correlation between two variables is tested / while controlling for a third
variable. / An example would be to test for the correlation between intoxication and
alcoholic intake / while controlling for body mass. (4 marks)"
"What does df stand for? - CORRECT ANSWER Degrees of Freedom (1 mark)"
"In statistical testing, what does the p value tell you? - CORRECT ANSWER When
used in the statistical sense, the p figure quoted states the probability of obtaining the
observed test result / if the null hypothesis is true. (2 marks)"
"Why is it conventional to opt for the .05 significance level in psychological research? -
CORRECT ANSWER The .05 level of significance is thought to strike a reasonable
balance between the probability of making a Type I or Type II error / in psychological
research that is not of 'life or death' importance. (2 marks)"
"What is a Type I error and how is it dealt with? - CORRECT ANSWER A Type I error
is an error of optimism / resulting from rejecting the null hypothesis when it should be
retained. / Such an error can be made less likely by choosing a more stringent
significance level. (3 marks)"
"What is a directional hypothesis and when would it be used? - CORRECT ANSWER A
directional hypothesis predicts the direction in which results will fall / e.g. the population
mean of sample A is higher than the mean of sample B / or the correlation between C
and D is positive. / Such hypotheses are used only when we have good reason to