Practise choosing and interpreting bar charts for categorical data, comparing category proportions, and rejecting claims that require unknown group totals.
A horticulturist plans a study on the use of compost tea for plant disease management. She obtains 18 identical beds, each containing a random selection of five minipink rose plants. Some bed or beds will not receive compost tea. For those beds receiving compost tea, she plans to use two different composting times (2 and 5 days), two different compost preparations (aerobic and anaerobic), and two different spraying techniques (with and without adjuvants). Midway into the growing season she will check all plants for rose powdery mildew disease.
Using the proportion of plants in each bed that are infected, identify an appropriate graphical representation.
Based on the bar chart, which of the following statements must be true?
Less than half of the students in the 10th grade indicated that they regularly rode the bus to school.
At least 20\% of students from each grade level indicated that they regularly rode the bus to school.
The number of students from the 9th grade who indicated that they regularly rode the bus to school is greater than the number of students from the 10th grade who indicated that they regularly rode the bus to school.
The 12th graders had the least number of students who indicated that they regularly rode the bus to school.
The 9th graders had the greatest percentage of students who indicated that they regularly rode the bus to school.
Three brands of candy pieces-X, Y, and Z-are made in many colors. Shaela bought one bag of each brand and counted the number of pieces of each color. The graph below shows the relative frequency distribution of colors for each bag.
■ Red
Which of the following statements must be true?
For Brand X, there were more green candy pieces than red candy pieces in the bag.
For Brand Y, there were more red candy pieces than green candy pieces in the bag.
There were more green candy pieces in the Brand X bag than were in the Brand Z bag.
There were the same number of blue candy pieces in the Brand X bag as were in the Brand Y bag.
The number of blue candy pieces in the Brand Z bag was equal to the sum of the number of blue candy pieces in the other two bags.