PS211 - Exam 2 - Z-test

assumptions for z-test

• randomly selected one sample and have sample mean

• DV: normally distributed on interval/ratio scale

• true pop mean is known

• true SD of population described by null is known

steps for performing z-test

• create sampling distribution of means

• choose alpha

  • .05

• identify region of rejection

  • direction

  • alpha

• identify critical value

  • z-value needed to reject null

z-crit

z-value needed to reject null

how to find z-crit

• identify direction

• z-table

statistical significance

observed result in data is unlikely to have occurred by random chance alone

when to reject the null

• less than - of z-crit

• greater than + pf z-crit

when to fail to reject the null

• greater than - of z-crit

• less than + of z-crit

when to use z-test

• sample mean

• population mean

• population SD