18 terms

PSY 360 Exam 4

random sample
requires (1) each individual in the population has an equal chance of being selected and (2) the probabilities must stay constant from one selection to the next if more than one individual is selected; it ensures there is no bias
sampling with replacement
ensures that the probability is not changing from one selection to the next
normal distribution
the commonly occuring shape for a population distribution which is symmetrical, with the mode in the middle and frequencies tapering off as you move towards either extreme
How can normal distribution be used to estimate probability?
when given the mean and standard deviation, we can use this information with the proportions for a normal distribution. Then we can determine the probabilities associated with specific samples by first turning the probability question into a proportion question
sampling error
the natural discrepancy or amount of error between a sample statistic and its corresponding population parameter
sampling distribution
a distribution of statistics obtained by selecting all the possible samples of a specific size from the population
distribution of sample means
the collection of sample means for all the possible random samples of a particular size (n) that can be obtained from a population
Central Limit Theorem
provides a precise description of the distribution that would be obtained if you selected every sample mean and consructed the distribution of the sample mean
hypothesis test
a statistical method that uses the data to evaluate a hypothesis about a population to see whether the treatment has an effect on the individuals in the population
null hypothesis
predicts that the treatment has no effect on the scores for the population and states that in the general population there is no impacts
alternative hypothesis
predicts that the treatment does indeed have an effect on the dependent variable and that there is an impact for the general population
chance probablity
the probabilty that your empirical results could be due to chance WHEN YOUR NULL HYPOTHESIS IS TRUE
critical value
The value of a statistic required in order to consider the results significant that leads us to reject Ho
Type I Error
reject Ho when Ho is true; saying the treatment has effect when it does not (false research published)
Type II Error
fail to reject Ho when Ho is false; study fails to detect a treatment effect that exists
statistical power
the probability of correctly rejecting Ho when false (1-ß=power); pre-defined by study investigators to reduce risk of type II error
one tailed test
A one-tailed test will test either if the mean is significantly greater than x or if the mean is significantly less than x
Under what conditions is a one-tailed hypothesis test appropriate?
when you first consider the consequences of missing an effect in the untested direction and conclude that they are negligible and using this test is not for the sole purpose of significance