Scope of Inference

A representative sample of 80 customers in a clothing store was surveyed about how they paid for their purchases. The table shows the responses. Based on the results, which of the following are valid inferences. Select all that apply.

• Tomorrow, 8 out of the first 80 customers will for sure pay with a gift card.

• In a group of 40 customers, it is expected that about 10 will pay with cash.

• About 0.3, or 30%, of all the store's customers will pay with a credit card.

• A sample of 100 customers would provide less reliable data.

Yadira wanted to estimate the mean number of words per page in a 180-page book she is reading. Which if these sampling methods gives the best estimate of the mean word count per page in the book?

• Count the words on one randomly chosen page.

• Calculate the mean word count for a sample consisting of the pages with pictures.

• Calculate the mean word count for a sample of 20 pages selected by choosing every 9th page.

• Calculate the mean word count for a sample consisting of the 10 pages that appear to have the most words.

Using your inference skills and proportional reasoning, predict the number of purple jellybeans in a bag of 200 total jellybeans if a random sample of 25 resulted in 4 purple jellybeans. I predict there will be _________ purple jellybeans.

The __________ ______ _______________ refers to the type of inferences that can be drawn from a study.

The manager of a music store surveyed a random sample of customer who shop in the store about their favorite type of music. The table shows the number of customers who selected each type of music. Based on the information in the table, which inference about the favorite type of music of all the customers who shop in the music store appears to be valid?

• They are certain to select rock or pop music.

• They are less likely to select country or rap music than rock music.

• They are more likely to select country music than jazz, classical, or rap music.

• They are certain to select any type of music other than jazz music.

The table shows the monthly sales at a pizza parlor for a 6-month period. Which statement is the best inference that can be made from the table?

• January had the lowest sales.

• The period with the greatest increase in monthly sales was from May to June.

• Sales for July will be greater than $10,000.

• The sales will drop over the next 2-month period.

A representative sample of 80 customers in a clothing store was surveyed about how they paid for their purchases. The table shows the responses. Based on the results, which of the following are valid inferences. Select two answer choices.

• Tomorrow, 8 out of the first 80 customers will for sure pay with a gift card.

• In a group of 40 customers, it is expected that about 10 will pay with cash.

• About 30% of all the store's customers will pay with a credit card.

• A sample of 100 customers would provide less reliable data.

The dot plots show the weights of a random sample of fish from two lakes. Pick the statement that describes the variability of the samples.

• The variability of the weights of the fish in Lake S is greater than the variability of the weights of the fish in Lake R.

• The variability of the weights of the fish in the two lakes are about the same.

• The variability of the weights of the fish in Lake R is greater than the variability of the weights of the fish in Lake S.

• You cannot determine variability based on a dot plot.

The table shows the finish times of 30 runners in the 100-meter dash. Use the table to identify the inference that can be made by comparing the measures of center.

• Every runner ran faster last year as compared to this year.

• Most runners ran faster last year, on average, as compared to this year.

• The runners ran faster this year, on average, as compared to last year.

• Every runner ran faster this year as compared to last year.

One week, Kyasia drove to work. The next week, she rode the train. Each day, she recorded how long it took in minutes. What can Kyasia infer from the two data sets?

• The time it take to get to drive to work is more consistent than the time it takes to take the train.

• Based on the mean, it generally takes longer to take the train to work.

• In terms of time, it is less consistent to drive than it is to take the train to work.

• It's impossible to make any inferences based on the data display.