Math Problem Statement

The table below shows my weight for the first few days after I was born. Let 𝑊W represent my weight, in ounces, at 𝑡t days old.

Day

Weight (ounces)

1

48

4

55

5

61

8

69

9

70

10

70

Demos ProTip: Did you know that you can copy and paste this table into Desmos?

a) Use technology and all the data points to calculate the regression ("best fit") linear model for 𝑊W. Round your result to the nearest hundredth.

𝑊=W= 

b) If I could leave the hospital when I weighed 5 pounds (80 ounces), according to your model, on what day was I allowed to go home (round to the nearest whole number)?

The model predicts that I was allowed to go home on day  .

c)I really went home on day 24. According to your model, how much did I weigh on day 24 (to the nearest whole ounce)?

The model predicts that on day 24 I weighed  ounces.

Solution

Let's go through this step-by-step:

a) Calculate the linear regression model for WW (weight in ounces) as a function of tt (days).

The data points we have are:

Day (tt)Weight (WW) (oz)
148
455
561
869
970
1070

To calculate the regression line W=mt+bW = mt + b (where mm is the slope and bb is the y-intercept), I will apply linear regression using the given points.

Let me compute that for you.The linear regression model for WW, based on the data, is:

W=2.63t+45.94W = 2.63t + 45.94

where:

  • m=2.63m = 2.63 is the slope (rate of weight gain per day),
  • b=45.94b = 45.94 is the y-intercept (initial weight at day 0).

b) When could you go home (i.e., weigh 80 ounces)?

To find the day tt when your weight reached 80 ounces, we use the equation: 80=2.63t+45.9480 = 2.63t + 45.94 Solving for tt.According to the model, you would have been allowed to go home on day 13.

c) Predicted weight on day 24

Now, let's use the model to predict your weight on day 24. We substitute t=24t = 24 into the equation: W=2.63(24)+45.94W = 2.63(24) + 45.94According to the model, your predicted weight on day 24 would have been 109 ounces.

Would you like any further details or explanations?

Here are 5 related questions you can explore:

  1. How would the model change if more data points were added?
  2. What does the slope represent in this context, and why is it important?
  3. Can a quadratic or another type of regression model better fit the data?
  4. What are some factors that could cause deviations from the predicted model in real life?
  5. How can you determine the accuracy of this regression model?

Tip: In statistics, checking the residuals of a regression model helps assess how well the model fits the data!

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Math Problem Analysis

Mathematical Concepts

Linear Regression
Algebra
Data Analysis

Formulas

W = mt + b (Linear Regression Equation)
Slope formula: m = (ΔW / Δt)
Linear equation solving for t

Theorems

Linear Regression Model

Suitable Grade Level

Grades 9-12