Scatter Plots

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PSAT Math › Scatter Plots

Questions 1 - 10
1

A scientist measured the amount of fertilizer applied to 11 plants and the resulting plant height after 6 weeks. The scatterplot shows fertilizer (grams) on the $x$-axis and height (centimeters) on the $y$-axis. A dashed line of best fit is included. What does the slope of the line of best fit represent in this context?

The total height increase for all plants combined.

The predicted increase in fertilizer (g) for each additional centimeter of height.

The predicted increase in plant height (cm) for each additional gram of fertilizer.

The plant height when fertilizer is $1$ gram.

Explanation

This question asks about the meaning of the slope in the context of fertilizer and plant height. In a scatterplot with fertilizer (grams) on the x-axis and height (cm) on the y-axis, the slope represents the change in y per unit change in x. Therefore, the slope tells us the predicted increase in plant height (cm) for each additional gram of fertilizer applied. A common error is reversing the interpretation (choice B) - remember that slope is always rise over run, or change in y over change in x. The slope does not represent a specific height value (choice C) or a total (choice D), but rather a rate of change.

2

A botanist recorded the amount of fertilizer used (grams) and the plant height after 4 weeks (centimeters) for 10 plants. The scatterplot includes a solid line of best fit. Which statement best describes the relationship between fertilizer and height shown in the scatterplot?

There is a strong negative association; more fertilizer generally means shorter plants.

There is a strong positive association; more fertilizer generally means taller plants.

There is no association; plant height stays about the same as fertilizer increases.

The plot proves fertilizer causes taller plants in all conditions.

Explanation

The question requires describing the relationship between fertilizer amount and plant height from the scatterplot with a solid line of best fit. The plot for 10 plants shows points trending upward, indicating a strong positive association where higher fertilizer levels correspond to taller plants, with the line of best fit having a positive slope and points clustered closely around it. This suggests that as fertilizer increases, height generally increases, supporting option B. The solution involves observing the direction and strength of the trend: positive due to the upward slope and strong because of minimal scatter. Avoid mistaking this for causation, as option D does, since scatterplots show correlation, not proof of cause; also, there's no evidence of negative or no association. Teach data literacy by noting that while the plot describes a pattern, inferences about causality require further experimentation. When interpreting, always distinguish between association strength and causal claims to avoid overgeneralizing.

3

A delivery company tracked the distance driven (miles) and total fuel used (gallons) for 9 routes. The scatterplot includes a line of best fit. What does the slope of the line of best fit represent in this context?

The estimated gallons of fuel used per mile driven.

The estimated miles that can be driven per gallon of fuel.

The estimated fuel used when the distance is 0 miles.

The estimated distance driven when fuel used is 0 gallons.

Explanation

The question interprets the slope of the line of best fit in the context of miles driven and fuel used for 9 routes. The scatterplot shows a positive trend with fuel used increasing as miles increase, and the line's slope represents the rate of change, specifically gallons per mile. This matches option A, as slope is rise over run: change in gallons divided by change in miles. The solution path involves recalling that in y = mx + b, m is the slope, here estimating fuel consumption per mile. Errors often occur by confusing slope with its reciprocal (miles per gallon, option B) or misinterpreting intercepts (options C and D). Emphasize data literacy by noting slopes describe average rates in context, but do not imply causation or apply beyond the data range. For such questions, always confirm units to ensure the interpretation matches the axes.

4

The scatterplot shows the age of a car (years) and its resale price (thousands of dollars) for 9 cars of the same model. A line of best fit is shown. For the car that is 6 years old, approximately how much greater is the actual price than the price predicted by the line of best fit?

0.5 thousand dollars

2.0 thousand dollars

1.0 thousand dollars

3.5 thousand dollars

Explanation

This question requires calculating the residual—the difference between actual and predicted resale price—for the 6-year-old car. The scatterplot of car age versus price for 9 cars shows a negative trend, with prices decreasing as age increases, and points varying around the line of best fit. For the 6-year-old car, the actual price is greater than predicted by about 2.0 thousand dollars, indicating a positive residual. Compute this by finding the predicted value on the line at x=6, subtracting from the actual y-value, and noting it's greater as asked. A common mistake is confusing greater with less or misidentifying the point, leading to wrong amounts like 1.0 or 3.5. Residuals teach data literacy by quantifying how well the line fits individual points, emphasizing description over causal inference. When analyzing, always specify if the residual is positive or negative to understand over- or under-prediction.

5

The scatterplot shows the number of text messages sent (messages) and the phone battery remaining after 6 hours (percent) for 11 days. A line of best fit is shown. Which statement is supported by the scatterplot?​

Battery percent tends to decrease as the number of messages sent increases.

Battery percent tends to increase as the number of messages sent increases.

Sending messages causes exactly a 10% battery drop every day.

Battery percent is constant, regardless of the number of messages sent.

Explanation

This question asks for a statement supported by the scatterplot of messages sent versus battery remaining for 11 days. The plot shows a negative trend with battery percent decreasing as messages increase, points scattered but following the downward line of best fit, indicating a moderate association. Option A is supported, as it describes the tendency without claiming causation or exactness. Analyze by noting the negative slope and dismissing constants or positives. Avoid errors like inferring causation (D) or ignoring the trend (C), as scatterplots show correlations, not causes. Teach careful interpretation: describe patterns factually, avoiding overstatements about causality. For such questions, eliminate options that imply proof or ignore the visual trend.

6

A researcher measured daily screen time (hours) and nightly sleep (hours) for 13 teenagers. The scatterplot shows a trend and includes a dashed line of best fit. Which statement about correlation and causation is most accurate based on the scatterplot?​

The plot proves increased screen time causes less sleep for all teenagers.

The plot suggests a negative association, but it does not prove screen time causes less sleep.

The plot suggests a positive association, so more screen time means more sleep.

The plot suggests no association because the points are not perfectly on a line.

Explanation

The question requires the most accurate statement about correlation and causation from the scatterplot of screen time versus sleep for 13 teenagers. The plot shows a negative association with sleep decreasing as screen time increases, points not perfectly linear but trending downward with the dashed line. Option B is correct, acknowledging the negative correlation without claiming causation. Determine this by observing the slope direction and recalling correlation does not imply causation. Common errors include assuming proof of cause (A) or misidentifying the association as positive (D) or none (C). Emphasize data literacy: scatterplots describe relationships, but causation needs controlled studies. Strategy: Always question if the statement confuses association with cause when evaluating options.

7

A store manager compared the price of a product to the number of units sold in 9 different weeks. The scatterplot (Price vs. Units Sold) shows a negative association. Which claim is supported by the scatterplot, without assuming causation?

Weeks with higher prices tend to be associated with fewer units sold.

Weeks with higher prices tend to be associated with more units sold.

Raising the price will always cause sales to drop by the same amount.

Price and units sold show no relationship in the data.

Explanation

This question asks which claim is supported by the scatterplot of price versus units sold, without assuming causation. The plot shows a negative association, with points trending downward, meaning higher prices link to fewer units sold across the weeks. Referencing the data pattern, the supported claim is that weeks with higher prices tend to be associated with fewer units sold, emphasizing correlation over cause. This avoids overreaching into causation like choice A. Common errors include assuming causation or misinterpreting the direction as positive (choice C) or none (choice D). Another mistake is implying constancy in the relationship, ignoring variability. When evaluating scatterplots, prioritize descriptive statements about associations to distinguish them from inferential claims in data literacy.

8

A school counselor recorded the number of hours 12 students studied for a math quiz and their quiz scores. The scatterplot (Hours Studied vs. Quiz Score) shows one point noticeably far from the general trend. A dashed line of best fit is drawn. Which data point is farthest from the line of best fit?

Approximately $(1, 58)$

Approximately $(4, 73)$

Approximately $(6, 60)$

Approximately $(2, 62)$

Explanation

This question asks which data point in the scatterplot of hours studied versus quiz score is farthest from the dashed line of best fit. The scatterplot displays a positive linear trend with points generally clustered around the line, but one point stands out as noticeably distant, indicating an outlier with a large residual. To identify the farthest point, examine the vertical distances from each data point to the line, as these residuals measure how far the actual quiz scores deviate from the predicted values. Among the given options, the point at approximately (6, 60) shows the largest vertical deviation from the line of best fit. A common error is confusing the farthest point with the one most distant from the origin or misjudging distances horizontally instead of vertically. Another mistake might involve ignoring the trend and selecting a point based solely on its position in the plot. When analyzing scatterplots, always focus on residuals perpendicular to the line to accurately assess fit, promoting careful interpretation of visual data over hasty inferences.

9

A researcher plotted the age of 13 used laptops (in years) against their resale price. The scatterplot (Age vs. Resale Price) includes a line of best fit. Using the line of best fit, what is the predicted resale price for a laptop that is $6$ years old?

About $210

About $160

About $260

About $110

Explanation

This question asks for the predicted resale price of a 6-year-old laptop using the line of best fit in the scatterplot of age versus price. The plot shows a negative linear trend with points decreasing as age increases, indicating older laptops have lower prices, with some variability. To predict, substitute 6 years into the line's model or visually locate the y-value, yielding about $160. This extrapolation assumes the trend continues moderately beyond the data. A common error is interpolating incorrectly or ignoring the downward slope, leading to overestimations like $210 or $260. Another mistake involves using average prices instead of the line. Focus on the line's direction and scale for predictions, teaching the importance of descriptive trends in visual data without over-inferring.

10

A city recorded the outside temperature and the number of hot chocolates sold at a café on 11 different days. The scatterplot (Temperature vs. Hot Chocolates Sold) suggests a roughly linear relationship with a trend line shown. Which statement best describes the relationship shown?

There is a strong negative association: hotter days are associated with fewer hot chocolate sales.

Temperature causes the exact number of hot chocolates sold each day.

There is no association: sales stay about the same across temperatures.

There is a strong positive association: hotter days lead to more hot chocolate sales.

Explanation

This question seeks the best description of the relationship between temperature and hot chocolates sold, as shown in the scatterplot. The plot indicates a roughly linear downward trend, with points decreasing as temperature rises, and the trend line confirms this negative association. To interpret, observe the overall pattern where higher temperatures correspond to fewer sales, without implying causation. The statement that hotter days are associated with fewer hot chocolate sales accurately captures this negative link. A frequent error is assuming the trend implies direct causation, like choice D, which oversteps into inference rather than description. Another mistake involves misreading the direction, such as claiming a positive association. Remember to describe associations in scatterplots without assuming cause-and-effect, fostering careful data literacy by distinguishing patterns from explanations.

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