Confidence Interval Calculator
Our advanced Loan Calculator helps you accurately determine monthly payments, total interest paid, and full amortization schedules for various loan types.
Calculation Type
Sample Information
Confidence Intervals
- • Higher confidence levels result in wider intervals
- • Larger sample sizes result in narrower intervals
- • The interval contains the true parameter with the specified confidence
- • Check assumptions before interpreting results
Confidence Interval
95% confidence
Margin of Error
±
Interval Width
Total width
Sample Statistic
Point estimate
Standard Error
SE
Distribution Information
Sample Size Analysis
How it works
A confidence interval gives a range that likely contains the true population value, based on your sample. It centers on the sample mean and extends a margin of error on each side, set by the confidence level, the variability in the data, and the sample size.
Confidence interval for a mean
CI = mean ± z · (σ ÷ √n)
- z
- z-score for the confidence level (1.96 for 95%)
- σ
- standard deviation
- n
- sample size
Worked example
- Mean = 100, σ = 15, n = 36
- 95% confidence (z = 1.96)
- Margin = 1.96 × (15 ÷ √36) = 1.96 × 2.5
- = 4.9
95% CI: 100 ± 4.9 → (95.1, 104.9).
Good to know
- A larger sample shrinks the interval — precision improves with √n, so 4× the data halves the margin.
- 95% confidence means that if you repeated the study many times, ~95% of such intervals would contain the true value.
- Use the t-distribution instead of z for small samples or unknown population variance.
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Frequently Asked Questions
How does this loan calculator work?
Our loan calculator uses standard financial formulas (e.g., for amortization) to compute your monthly payments, total interest, and total amount repayable. Simply input your principal loan amount, interest rate, and loan term, and it will generate a detailed breakdown.
What is an amortization schedule?
An amortization schedule is a table detailing each periodic loan payment, showing the amount of principal and interest contained within each payment until the loan is paid off. It helps you see how your principal balance decreases over time.
Can I use this for different loan types?
Yes, this calculator is versatile enough for various loan types including personal loans, car loans, student loans, and even small business loans. Just ensure you input the correct principal, interest rate, and term for your specific loan.