Reading a two-way frequency table
A grid of counts. Every probability on it is one number over another, and the only skill is knowing which two. Two questions on Exam 1 of this unit depend on it.
A short walkthrough explaining what you need to know and how to solve this question type lands here once it's recorded.
ALEKS randomizes the numbers each attempt, but the question shape stays the same. Here are three example versions you might see.
Of 198 employees, preferences by gender are:
Male: 52 shirt, 93 jacket. Female: 43 shirt, 10 jacket.
One employee is chosen at random. What is the probability they prefer a jacket? Round to the nearest hundredth.
Same 198 employees. Male: 52 shirt, 93 jacket. Female: 43 shirt, 10 jacket.
What is the probability the employee is female or prefers a jacket? Round to the nearest hundredth.
195 adults were classified by voter registration and preferred news source.
Registered: 16 television, 17 newspapers, 33 radio, 37 internet.
Not registered: 23 television, 16 newspapers, 34 radio, 19 internet.
What is the relative frequency of adults who are registered and prefer radio? Round to two decimal places.
A hundred people at a conference were asked their role and their drink.
One person is chosen at random. Round answers to the nearest hundredth.
A single cell
A margin
The or, with the overlap removed
The check that catches it
Adding without subtracting gives 1.07. A probability cannot exceed 1, so that answer announces its own error.
Whenever an “or” answer comes out above 1, you have forgotten the overlap. It is the only common way to produce an impossible probability, and it is worth checking every time.