psych stats
to construct a sampling distribution you must
(1) identify the mean of the sampling distribution (2) compute the standard error of the mean (3) distribute the possible sample means 3 SEM above and below the mean.
3 characteristics of the sample mean
-is an unbiased estimator -follows central limit theorem -has a minimum variance
standard error calculated
-is the population standard deviation divided by the square root of the sample size.
h1
alternative hypothesis
law of large numbers
increasing the number of observations or samples size will decrease standard error. the smaller the standard error, the closer a distribution of sample means will be from the population mean
cohen's d
measures the number of standard deviations an effect an effect shifted above or below the population mean stated by the null hypothesis.
standard error
standard deviation of sample means is measured by the _____ of the mean.
effect
difference between sample mean and population mean stated in null hypothesis
type 2
failure to reject a false hypothesis.
N! / n! (N-n)!
formal for determining the number of samples of any size that can be selected from a population
one tailed tests
greater power. if value stated in null hypothesis is false, this test will make it easier to detect and reject. but difficult to justify. do not double for this
type 1
incorrect rejection of a true null hypothesis
characteristics of the sample variance
-it is an unbiased estimator when we divided SS by df (or n-1) -distribution of this follows the skewed distribution rule -distributions of this has no minimum variance when we divide SS by df
sample variance
-the ___________ is an unbiased estimator when we divided SS by df (or n - 1) -distribution of the sample variances follows the skewed distribution rule -distribution of sample variances has no minimum variance when we divided SS by df.
sampling distributions
a distribution of all the sample means or variances that could be obtained in samples of a given size from the same population
vary far
although the sample variance equals the population variance on average, the distribution of all other sample variances can _________ from the population variance when you divided SS by df.
experimental theory is for
behavioral research
level of significance
criterion of judgement upon which a decision is made regarding the value stated in the null
compute the test statistic
is step 3 of hypothesis testing. the value of it can be used to make a decision regarding null hypothesis. helps determine how likely the sample outcome is if the population mean stated in the null is true.
two tailed tests
more conservative more difficult to reject null hypothesis eliminates possibility of type III error
h0
null hypothesis
standard deviation
of sample means is measured by the standard error of the mean. is calculated by the square root of the variance.
what do you not double p value
one tailed tests.
central limit theorem
regardless of the distribution of sample means selected from that population will be approximately normally distributed.
effect size
size of an effect in a population -how far scores have shifted in the population -percent of variance that can be explained by a given variable -most meaningfully reported with significant effects (decision to reject null)
as population standard deviation decreases
standard error decreases
as sample size increases
standard error decreases
null hypothesis
statement about the population parameter (such as the mean) that is assumed to be true. -starting point to determine if null is likely to be true or not. example: children in the united states watch an average of 3 hours of TV per week
alternative hypothesis
statement that contradicts the hypothesis we think null is wrong, allows us to state what we think is right
theoretical theory is for
statistical theory
variance
the _______ of the sampling distributions of the sample means is minimal.
smaller the standard error
the closer a distribution of sample means will be from the population mean
sampling error
the extent to which sample means selected from the same population differ from one another.
experimental sampling
the order of selecting individuals does not matter and each individual selected is not replaced before sampling again used in behavioral research
theoretical sampling
the order of selecting individuals matters an each individual selected is replaced before sampling again basis for statistical theory
reject null when
the sample mean is less than 5%,
skewed distribution rule
the sampling distribution of sample variances tends toward a positively skewed distribution, regardless of the distribution in the population.
normal distribution
the theoretical distribution with data that are symmetrically distributed around the mean, median and mode
5%
what the level of significance is usually set as
