Statistical method & guardrails — found from sitemap — Plerdy

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Facts read from this source

• Calculator purpose Report an error

  “Use this sample size calculator to determine how many observations or completed responses you need for reliable research. Enter the population size, confidence level, and margin of error to calculate the recommended sample size.”

• Default proportion Report an error

  “When the expected population proportion is unknown, the calculator uses 50%. This is the most conservative assumption because it produces the largest recommended sample size.”

• Inputs required Report an error

  “To calculate sample size, enter three values: population size, confidence level, and margin of error.”

• Confidence range Report an error

  “Confidence Level (%) 80 99 0.00”

• Result meaning Report an error

  “The calculated result represents completed and usable observations. If you are conducting a survey, it does not represent the number of invitations you need to send.”

• Reference table Report an error

  “Margin of Error 90% Confidence 95% Confidence 99% Confidence ±10% 68 97 166 ±5% 271 385 664 ±3% 752 1,068 1,844 ±2% 1,692 2,401 4,145 ±1% 6,765 9,604 16,588”

• Population table Report an error

  “Population Size Required Sample Size 100 80 300 169 500 218 1,000 278 5,000 357 10,000 370 100,000 383 Large or Unknown 385”

• Formula Report an error

  “n0 = Z2 × p × (1 − p) / e2”

• Z scores Report an error

  “Confidence Level Z-Score 80% 1.282 90% 1.645 95% 1.960 99% 2.576”

• Finite population correction Report an error

  “n = n0 / (1 + (n0 − 1) / N)”

• Invitation formula Report an error

  “Invitations needed = Required sample size / Expected response rate”

• Method assumptions Report an error

  “Method: population-proportion sample size formula with finite population correction. Expected population proportion: 50%. Sampling assumption: simple random sampling. Observation assumption: observations are independent. Result: minimum recommended sample size rounded up to a whole number. Scope: quantitative studies estimating a population proportion.”

• Last reviewed Report an error

  “Last reviewed: August 2026.”

• Related calculators Report an error

  “More calculators TikTok Money Calculator CPM Calculator Facebook Ads Cost Calculator ROMI Calculator ROI Calculator NPS calculator CTR Calculator CAC Calculator UTM Builder”

• Trial offer Report an error

  “Start free trial”

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• The CRO Consultant Statistical method & guardrails
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