Math Problem Statement

Please answer this

A small animal veterinarian reviews her records for the day and notes that she has seen eight dogs and eight cats with the following weights (in pounds): Dogs: 14, 21, 36, 45, 55, 64, 78, 102 Cats: 3, 3, 6, 8, 11, 14, 18, 28 (a) Before analyzing the data sets, make a conjecture about which set has the larger mean, median, and standard deviation. Explain your reasoning. (b) Compute the mean and standard deviation of each set.

Solution

From the question, let's compute the requested values step-by-step.

Given Data:

Dogs' weights: 14, 21, 36, 45, 55, 64, 78, 102
Cats' weights: 3, 3, 6, 8, 11, 14, 18, 28


Step 1: Compute Mean (Average)

Formula for Mean:
Mean=Sum of all weightsNumber of animals\text{Mean} = \frac{\text{Sum of all weights}}{\text{Number of animals}}

Dogs' Mean: Sum of dogs’ weights=14+21+36+45+55+64+78+102=415\text{Sum of dogs' weights} = 14 + 21 + 36 + 45 + 55 + 64 + 78 + 102 = 415
Mean=4158=51.875\text{Mean} = \frac{415}{8} = 51.875

Cats' Mean: Sum of cats’ weights=3+3+6+8+11+14+18+28=91\text{Sum of cats' weights} = 3 + 3 + 6 + 8 + 11 + 14 + 18 + 28 = 91
Mean=918=11.375\text{Mean} = \frac{91}{8} = 11.375


Step 2: Compute Standard Deviation

Formula for Standard Deviation:
SD=(xmean)2n\text{SD} = \sqrt{\frac{\sum{(x - \text{mean})^2}}{n}}

Dogs' Standard Deviation:

  1. Compute deviations: (xmean)(x - \text{mean}): 1451.875,2151.875,3651.875,,10251.87514 - 51.875, \, 21 - 51.875, \, 36 - 51.875, \, \dots, \, 102 - 51.875 Square these deviations and sum them up: Sum of squared deviations=1487.109375\text{Sum of squared deviations} = 1487.109375
  2. Divide by n=8n = 8, then take the square root: SD=1487.1093758=13.60\text{SD} = \sqrt{\frac{1487.109375}{8}} = 13.60

Cats' Standard Deviation:

  1. Compute deviations: (xmean)(x - \text{mean}): 311.375,311.375,611.375,,2811.3753 - 11.375, \, 3 - 11.375, \, 6 - 11.375, \, \dots, \, 28 - 11.375 Square these deviations and sum them up: Sum of squared deviations=382.875\text{Sum of squared deviations} = 382.875
  2. Divide by n=8n = 8, then take the square root: SD=382.8758=6.90\text{SD} = \sqrt{\frac{382.875}{8}} = 6.90

Step 3: Analyze Median and Spread

Dogs' Median:

  • Sort weights: 14, 21, 36, 45, 55, 64, 78, 102
  • Middle values: 45, 55
  • Median = 45+552=50\frac{45 + 55}{2} = 50

Cats' Median:

  • Sort weights: 3, 3, 6, 8, 11, 14, 18, 28
  • Middle values: 8, 11
  • Median = 8+112=9.5\frac{8 + 11}{2} = 9.5

Final Conjectures:

  1. Dogs have a higher mean (51.875 vs. 11.375), median (50 vs. 9.5), and standard deviation (13.60 vs. 6.90).
  2. The spread in dogs’ weights is higher because their weights vary more widely.

Let me know if you want further clarification or deeper delving into any part!
Here are five related questions for you to think about:

  1. What causes the larger spread in the dogs' weights?
  2. How might a larger spread influence decision-making in a veterinary context?
  3. Could outliers affect these calculations significantly?
  4. How is variance related to standard deviation?
  5. Why is the median less affected by outliers than the mean?

Tip: Always double-check your computation steps for accuracy, especially for mean and standard deviation!

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Math Problem Analysis

Mathematical Concepts

Statistics
Mean
Median
Standard Deviation
Data Analysis

Formulas

Mean = Sum of all values / Number of values
Standard Deviation = sqrt((Σ(x - mean)^2) / n)

Theorems

Properties of central tendency and variability

Suitable Grade Level

Grades 9-12