Algebra 1 Scatter Plots, Lines of Fit and Two-Way Tables Quiz: 10 Questions with Explanations

A Negative associationB Positive associationC No associationD Perfect correlation

The points go down as x increases.

A The plant starts at 1.5 cmB The plant grows about 1.5 cm per dayC The plant grows 4 cm per dayD The plant is 1.5 cm after 4 days

The slope is the rate of change: the predicted height rises 1.5 cm for each day.

A The plant grows 4 cm per dayB The plant stops growing at 4 cmC The plant is 4 days oldD The predicted height at day 0 is 4 cm

The y-intercept is the predicted value when x = 0.

A 3B -3C 17D 37

Residual = actual – predicted = 20 – 17 = 3.

A The left panel (positive)B The middle panel (negative)C All three panelsD The right panel (none)

The right panel’s points are scattered with no linear trend, so r is near 0.

A A weak negative linear relationshipB A strong negative linear relationshipC A strong positive linear relationshipD No linear relationship

The sign is negative, so y tends to decrease as x increases, and 0.9 is close to 1, so the relationship is strong.

A Buying sunscreen causes people to buy sunglassesB Buying sunglasses causes people to buy sunscreenC A lurking variable such as sunny weather may explain bothD The correlation must be a mistake

Correlation does not prove causation. Sunny weather increases both.

A 30%B 60%C 28%D 45%

Among the 30 boys, 18 prefer dogs: 18/30 = 60%. Dividing by the grand total gives the joint frequency 30%.

A Extrapolation, which can be unreliableB Interpolation, which is reliableC A residualD A correlation

Predicting far outside the range of the data is extrapolation.

A -2B 7C 2D 9

The predicted value at x = 3 is 7, so the residual is 9 – 7 = 2. Points above the line have positive residuals.