# Repairable vs Non-repairable Products

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## Non-repairable Items

The term 'non-repairable' refers to products that cannot be repaired after they've broken down or the repair is not cost-effective. Some examples of non-repairable items in daily life are light bulbs, calculators etc.

The reliability of non-repairable items is the likelihood (probability) that an item will survive a given time interval without failing. In this case, we are looking at the probability of the first failure as the item is non-repairable.

A common measure of reliability for non-repairable products is the Mean Time to Failure (MTTF).

<a class="thirstylink" target="_blank" title="re" href="https://www.qualitygurus.com/link/re/" data-shortcode="true">MTTF</a> <a class="thirstylink" target="_blank" title="calc" href="https://www.qualitygurus.com/link/calc/" data-shortcode="true">Calculator</a> for Non-Repairable Items

## Mean Time To Failure (MTTF) Calculator

``` function addFailureTimeField() { const numItems = parseInt(document.getElementById('numItems').value); const inputFields = document.getElementById('inputFields'); if (isNaN(numItems) || numItems <= 0) { alert('Please enter a valid number of items.'); return; } if (inputFields.children.length >= numItems) { alert('Number of failure times cannot exceed the number of items.'); return; } const fieldNumber = inputFields.children.length + 1; const fieldDiv = document.createElement('div'); fieldDiv.className = 'input-field'; fieldDiv.innerHTML = ` <label>Failure Time \${fieldNumber}: </label> <input type="number" step="any" min="0" class="failureTime"> `; inputFields.appendChild(fieldDiv); } function calculateMTTF() { const numItems = parseInt(document.getElementById('numItems').value); const testTime = parseFloat(document.getElementById('testTime').value); const failureTimes = document.getElementsByClassName('failureTime'); let totalFailureTime = 0; let failedItems = 0; if (isNaN(numItems) || numItems <= 0 || isNaN(testTime) || testTime <= 0) { alert('Please enter valid numbers for number of items and test time.'); return; } for (let i = 0; i < failureTimes.length; i++) { const failureTime = parseFloat(failureTimes[i].value); if (isNaN(failureTime) || failureTime > testTime) { alert('Please enter valid failure times, each not exceeding the test time.'); return; } totalFailureTime += failureTime; failedItems++; } const mttf = (totalFailureTime + (numItems - failedItems) * testTime) / numItems; document.getElementById('result').innerHTML = `Mean Time To Failure (MTTF): \${mttf.toFixed(4)} units`; } ```

## Repairable Items

The term 'repairable' refers to products that can be repaired economically after breaking down, or the repair costs significantly less than the original price. Examples include a car, washing machine and dishwasher.

The reliability of repairable items is the probability that the failure will not occur in the specified period of interest. Repairable items can have multiple repairs over their period of use.

A common measure of reliability for repairable products is the Mean Time Between Failures (MTBF).

## Type I and Type II Errors Explained

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