STATISTICS PORTAGE EXAM 5 QUESTIONS WITH COMPLETE SOLUTIONS

STATISTICS PORTAGE EXAM 5
QUESTIONS WITH COMPLETE
SOLUTIONS
Using the z-test requires that we know... - ANSWERstandard deviation

When the standard deviation is unknown, we estimate it using... - ANSWERthe sample
standard deviation (s)

When we use s instead of σ, the distribution of the sample means is no longer ____. -
ANSWERnormal

Instead of the normal distribution, the distribution of sample means when σ is estimated
using s follows a... - ANSWERt distribution (aka student distribution)

The t distribution is... - ANSWERsymmetrical with most scores centered around the
mean

The shape of the t distribution changes depending on the... - ANSWERdegrees of
freedom

degrees of freedom - ANSWERthe number of scores in the sample that are
independent

degrees of freedom formula - ANSWERdf= n-1

As sample size increases, degrees of freedom ____ and the variability in sample means
____. - ANSWERincreases, decreases

one sample t-test - ANSWERcompares one sample mean against the population mean

How many critical values are there for a 2-tailed test? - ANSWER2; one positive and
one negative

How many critical values are there for a 1-tailed test? - ANSWER1; it may be positive or
negative

t-test statistic formula - ANSWERt=(X̄- μ)/s(X̄)

s(X̄)= - ANSWERs/squareroot(n)

It is generally easier to reject the null hypothesis with... - ANSWERone tailed tests