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Identify the error in this code for calculating a 95% confidence interval:

medium📝 Debug Q6 of 15
SciPy - Curve Fitting and Regression
Identify the error in this code for calculating a 95% confidence interval:
from scipy.stats import t
sample = [4, 5, 6, 7, 8]
mean = sum(sample)/len(sample)
std_err = (sum((x - mean)**2 for x in sample)/len(sample))**0.5 / len(sample)**0.5
df = len(sample) - 1
ci = t.interval(0.95, df, loc=mean, scale=std_err)
print(ci)
At.interval requires scale to be variance, not standard error
BStandard error calculation uses population variance denominator instead of sample
CDegrees of freedom should be len(sample), not len(sample) - 1
DMean calculation is incorrect
Step-by-Step Solution
Solution:
  1. Step 1: Check standard error formula

    Standard error should use sample variance denominator (n-1), not n.
  2. Step 2: Identify denominator in variance calculation

    Code uses len(sample) instead of len(sample)-1, causing bias.
  3. Final Answer:

    Standard error calculation uses population variance denominator instead of sample -> Option B
  4. Quick Check:

    Variance denominator error = Standard error calculation uses population variance denominator instead of sample [OK]
Quick Trick: Use n-1 for sample variance in std error [OK]
Common Mistakes:
  • Using population variance denominator
  • Confusing degrees of freedom
  • Misusing scale parameter

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