Type I and II Errors What are type I and II errors and what do they mean?

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Presentation transcript:

Type I and II Errors What are type I and II errors and what do they mean?

You never really know the truth about the Null Hypothesis, all you really know is what your sample tells you. We never really are sure if we make mistakes or not when we reject or fail to reject the Ho So, we measure the probability that we might make a mistake. We give the two possible mistakes names: Type I and Type II The truth about the Null

There are 4 possible outcomes with a hypothesis test. Pg 1.2 You Fail to Reject the Null Hypothesis & it is true – youre right! You Fail to Reject the Null Hypothesis & it is false – youre wrong You Reject the Null Hypothesis & it is true – youre wrong! You Reject the Null Hypothesis & it is false – youre right!

Put in table format it looks like this.

Beads! You have been given a sample of beads. Pick a color to test – every one at your table must pick a different color – and count how many of the beads are your color. The company says they make 25% of each color bead. Set up a Hypothesis test to test their claim. Pg 1.4 choose color Pg 1.5 count – find phat

Beads! Hypothesis in picture format The company says they make 25% of each color bead. Set up a Hypothesis test to test their claim with your color bead Population for Ho Sample P-value C.I. - % certain that Population % falls in this interval

Beads! You have been given a sample of beads. Pick a color to test – every one at your table must pick a different color – and count how many of the beads are your color. The company says they make 25% of each color bead. Set up a Hypothesis test to test their claim. Find Assumptions:Hypothesis Statement Find Assumptions:Hypothesis Statement Null Hypothesis:Alternate Hypothesis Find Assumptions:Hypothesis Statement Null Hypothesis:Alternate Hypothesis Critical value:Alpha Level: Find Assumptions:Hypothesis Statement Null Hypothesis:Alternate Hypothesis Critical value:Alpha Level: Z-score:P-value for test: Find Assumptions:Hypothesis Statement Null Hypothesis:Alternate Hypothesis Critical value:Alpha Level: Z-score:P-value for test: Conclusion: Pg 1.6 assumptions Pg 1.7 Ho & Ha Pg 1.8 alpha Pg 1.9 z & p-value Pg 1.10 error type

Beads! Which type of error might you have made? Explain it in context.

The definitions as pictures applet

A company manufacturing computer chips finds that 8% of all chips manufactured are defective. Management is concerned that employee inattention is partially responsible for the high defect rate. In an effort to decrease the percentage of defective chips, management decides to offer incentives to employees who have lower defect rates on their shifts. The incentive program is instituted for 1 month. If successful, the company will continue with the incentive program.