Prepare values with the same meaning
Before calculating, check that every value measures the same quantity in the same unit. Mixing minutes and seconds or measurements from different groups can produce a plausible number that does not answer your question. Identify missing observations as well: replacing an absence with zero changes the calculation rather than merely completing a list.
List statistics accepts numbers separated by spaces, line breaks or semicolons. Both commas and periods can be decimal separators, without thousands separators. Put one value per line when interpretation is unclear. Up to ten thousand values produce a sum, mean, median, minimum and maximum. Keep the source list for checking any unexpected summary.
Compare mean and median using a small case
The mean divides the sum by the number of values. The median is the middle value after sorting; an even count uses the average of the two central values. For 2, 4 and 100, the mean is approximately 35.33 and the median is 4. The high value therefore has a substantial influence on the mean.
Neither number describes the entire distribution. Review count, minimum and maximum and preserve the underlying observations. Repetitions count as additional observations; do not remove duplicates when each represents a real measurement. Choose a statistic for the question you need to answer rather than because one output looks more convenient or reassuring.
Use weights when contributions differ
Weighted average takes one value;weight pair per line. It divides the sum of each value multiplied by its weight by the sum of weights. Entering 8;40 and 6;60 gives 6.8, unlike the simple average of 8 and 6, which is 7. Define what the weight represents before applying this formula.
Weights can be quantities, percentages or proportions and do not have to sum to one hundred. Multiplying all weights by the same constant preserves the average. They must be nonnegative with at least one positive weight. A zero weight does not contribute to the average, although the row still counts as an input entry.
Check the average and retain its assumptions
With positive weights, the result should lie between the minimum and maximum of contributing values. Try equal weights to check that the simple mean is recovered. If you intended percentages, inspect their total separately: the tool accepts other weight meanings and cannot know which convention your activity requires.
Avoid rounding each product before calculation. Save the displayed average with its unit and sufficient precision for the task; presentation rounding does not change the source observations. Retain inputs, exclusions and weight meanings. If a result is unexpected, investigate decimal interpretation, missing values and units first, then reconsider whether the selected formula matches the question you intended to answer.
The same values with different weights
Enter both pairs in Weighted average: the first number is the value and the second its weight. Calculate, then change weights to 4 and 6 while retaining values 8 and 6.
8;40 6;60
Both versions give 6.8. Weights retain the same proportion, 40:60 and 4:6. The simple mean of 8 and 6 is 7 because contributions are equal.
In List statistics, try 2, 4 and 100, one per line. Mean is approximately 35.33 and median is 4. Preserve the meaning of observations before choosing a summary.