Math Problem Statement

Tapi aku pake rumus s nya itu 1/n dikali akar n kali sigma x1 pangkat 2 di kurang (sigma x1) pangkat 2 per n -1

Pengukuran diameter bola pejal menggunakan jangka sorong dilakukan secara berulang dan dihasilkan data sebagai berikut. Penulisan diameter bola pejal beserta ketidakpastiannya yang benar adalah ....

Solution

To solve this problem, you want to calculate the correct average diameter of the solid sphere and its uncertainty based on the given measurements. The formula for calculating the uncertainty (standard deviation of the mean) is typically derived from statistical principles. Let's break this down step by step.

Step 1: Calculate the Mean Diameter

Given measurements of the sphere's diameter:

  • 8.15 cm
  • 8.10 cm
  • 8.00 cm
  • 8.15 cm
  • 8.00 cm

The mean xˉ\bar{x} is given by:

xˉ=xin\bar{x} = \frac{\sum x_i}{n}

Where xix_i are the measurements, and n=5n = 5 (the number of measurements).

xˉ=8.15+8.10+8.00+8.15+8.005=40.405=8.08cm\bar{x} = \frac{8.15 + 8.10 + 8.00 + 8.15 + 8.00}{5} = \frac{40.40}{5} = 8.08 \, \text{cm}

Step 2: Calculate the Standard Deviation

The formula for the standard deviation ss is:

s=(xixˉ)2n1s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n-1}}

First, compute (xixˉ)2(x_i - \bar{x})^2 for each measurement:

  • For x1=8.15x_1 = 8.15, (8.158.08)2=0.0049(8.15 - 8.08)^2 = 0.0049
  • For x2=8.10x_2 = 8.10, (8.108.08)2=0.0004(8.10 - 8.08)^2 = 0.0004
  • For x3=8.00x_3 = 8.00, (8.008.08)2=0.0064(8.00 - 8.08)^2 = 0.0064
  • For x4=8.15x_4 = 8.15, (8.158.08)2=0.0049(8.15 - 8.08)^2 = 0.0049
  • For x5=8.00x_5 = 8.00, (8.008.08)2=0.0064(8.00 - 8.08)^2 = 0.0064

Now, sum the squared deviations:

(xixˉ)2=0.0049+0.0004+0.0064+0.0049+0.0064=0.023\sum (x_i - \bar{x})^2 = 0.0049 + 0.0004 + 0.0064 + 0.0049 + 0.0064 = 0.023

Then calculate the standard deviation:

s=0.02351=0.0234=0.00575=0.0758s = \sqrt{\frac{0.023}{5-1}} = \sqrt{\frac{0.023}{4}} = \sqrt{0.00575} = 0.0758

Step 3: Calculate the Uncertainty (Standard Error of the Mean)

The uncertainty Δx\Delta x (standard error of the mean) is given by:

Δx=sn=0.07585=0.07582.2360.034cm\Delta x = \frac{s}{\sqrt{n}} = \frac{0.0758}{\sqrt{5}} = \frac{0.0758}{2.236} \approx 0.034 \, \text{cm}

Step 4: Final Answer

The correct way to write the diameter with its uncertainty is:

(8.08±0.034)cm(8.08 \pm 0.034) \, \text{cm}

This corresponds to option e.


Do you have any questions or need further details? Here are some related questions:

  1. How would the uncertainty change if more measurements were taken?
  2. Why do we use n1n-1 in the standard deviation formula?
  3. How can you interpret the significance of the uncertainty value?
  4. What are other ways to measure uncertainty in experimental data?
  5. What if one of the measurements was significantly different, how would that impact the results?

Tip: Always double-check your calculations for the mean and standard deviation, as small errors can impact the final uncertainty result.

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Math Problem Analysis

Mathematical Concepts

Statistics
Measurement Uncertainty
Standard Deviation
Mean

Formulas

Mean: \(\bar{x} = \frac{\sum x_i}{n}\)
Standard Deviation: \(s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n-1}}\)
Uncertainty: \(\Delta x = \frac{s}{\sqrt{n}}\)

Theorems

Standard Deviation Theorem
Measurement Uncertainty

Suitable Grade Level

Grades 10-12