TWO WAY

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# TWO WAY - PowerPoint PPT Presentation

TWO WAY. TABLES. Task One – Data Collection. What is the probability that…. A student has an Ipod? A student has been to the SI? A student does not have an Ipod? A student has not been to SI? A student has an Ipod and has been to the SI? A student has an Ipod or has been to SI)

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Presentation Transcript

TWO WAY

TABLES

What is the probability that…
• A student has an Ipod?
• A student has been to the SI?
• A student does not have an Ipod?
• A student has not been to SI?
• A student has an Ipod and has been to the SI?
• A student has an Ipod or has been to SI)
• A student does not have an Ipod or has not been to the SI?
Same same but different??
• If we know they have an Ipod, what is the probability they have been to South Island?
• If we know they have been to the South Island what is the probability they have an Ipod?
What is the probability that…
• A student is blonde?
• A student spent less than 2 hours watching TV last night?
• A student is blonder and spent more than 2 hours watching TV last night?
• A blonde student spent less than 2 hours watching TV last night?
• A student who was watching TV for more than 2 hours last night is blonde?
Questions?
• Write your own set of at least 5 questions you could answer using the previous two-way table.
Fill in the gaps

110

130

295

595

Design your own two way table

Write 5 probability questions to go with your table

Medical diagnosis
• A patient has a test to see if they have or do not have a particular disease
• The test gives a result – either positive or negative
Definitions
• False Positive
• A healthy person is told they have the disease
• False Negative
• A person with the disease is told they don’t have it
Further definitions
• Sensitivity
• Probability that a person who has the disease gets a positive result
• Closer it is to 1 the better the test is at determining if a person has the disease
• Specificity
• Probability that a person who does not have the disease gets negative result
• Closer it is to 1 the better the test is at determining if a person does not have the disease
Questions
• Calculate the probability of a false positive
• Calculate the probability of a false negative
• Calculate the specificity and sensitivity of this test
• How effective is this test?
Questions
• Calculate the probability of a false positive
• Calculate the probability of a false negative
• Calculate the specificity and sensitivity of this test
• How effective is this test?
Questions
• Calculate the probability of a false positive
• Calculate the probability of a false negative
• Calculate the specificity and sensitivity of this test
• How effective is this test?
Design your own 3 way table

Write 5 probability questions to go with your table

Thinking flexibly
• What other contexts do you think two way tables would be useful in?