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A/B Testing Total File Size vs File Size Per Variant

Compare total A/B test data volume with average per-variant file size and see how traffic allocation, variants, events, and compression affect each measure.

Total file size and average file size per variant answer different planning questions. The total reflects all experiment event data, while the per-variant average shows a theoretical split when traffic is evenly allocated. Both should be interpreted alongside event volume and compression assumptions.

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About A/B Testing Total File Size vs File Size Per Variant

Total file size and average file size per variant answer different planning questions. The total reflects all experiment event data, while the per-variant average shows a theoretical split when traffic is evenly allocated. Both should be interpreted alongside event volume and compression assumptions.

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Key Factors

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1

Total experiment size vs average size per variant

Compare the two primary data-volume outputs for an evenly allocated experiment.

FactorOption A: Total File SizeOption B: Average File Size per VariantWhat It Means
What it measuresAll compressed event data across the experiment.Total compressed event data divided by the number of variants.The useful measure depends on whether planning is for the full experiment or an individual group.
Participant allocationUses every participant regardless of group assignment.Assumes equal allocation among variants.The total remains useful even when traffic is uneven, while the average may not represent a specific group.
Storage planningUseful for combined datasets, exports, and total capacity.Useful for estimating group-level partitions under an even split.Storage architecture determines whether total or partition-level volume matters more.
Effect of more variantsUnchanged if total participants and behavior stay constant.Decreases because the same total is divided among more groups.Neither result is inherently better; they describe different views of the same data.
Risk of misinterpretationCan hide that one variant has much more traffic than another.Can be mistaken for the actual size of every variant.Review allocation assumptions before using either value for detailed capacity planning.

Use total file size for overall data-volume planning. Use average size per variant only as an even-split reference, not as a guarantee for each variant.

2

Compact event schema vs detailed event schema

Compare two tracking designs with the same traffic but different average event sizes.

FactorOption A: Compact EventsOption B: Detailed EventsWhat It Means
Average event sizeFewer or shorter properties generally reduce record size.More properties, nested data, or long values generally increase record size.Smaller raw records usually lower per-user and total volume.
Per-user data volumeLower when event counts are the same.Higher when event counts are the same.Per-user volume scales directly with average event size.
Compression potentialMay compress well if fields are repetitive.May also compress well, but unique payload values can limit reduction.Compression depends on content patterns, not simply on raw record size.
Analysis detailMay omit context needed for some analysis.Can retain more contextual information.Data needs and volume should be considered together.
Export and transfer timeTypically lower for the same number of participants and events.Typically higher for the same number of participants and events.Larger files can require more time and bandwidth to move.

Average event size is a direct driver of estimated file size. A compact schema lowers volume, while a detailed schema may support broader analysis needs.

3

Low compression vs high compression assumptions

Compare file-size estimates under different compression reductions.

FactorOption A: Low Compression ReductionOption B: High Compression ReductionWhat It Means
Remaining raw dataA larger share of raw data remains.A smaller share of raw data remains.A higher reduction produces a smaller compressed estimate.
Estimated file sizeHigher for identical raw data.Lower for identical raw data.Compressed size equals raw size multiplied by the remaining data share.
Reliability of assumptionMay be more conservative when no measured rate is available.May be appropriate when validated by representative files.The best assumption is one supported by the intended format and actual payload characteristics.
Effect of unique valuesLess sensitive to overestimating compression benefits.Can be optimistic if records contain many unique values.Unique identifiers, timestamps, and varied text can reduce compression efficiency.
Planning useUseful as a cautious capacity scenario.Useful as an observed-performance scenario.Comparing both can show a reasonable planning range.

Compression has a direct, proportional effect on the estimate, but the reduction rate should be treated as an assumption unless measured on representative data.

Key Differences at a Glance

Total file size includes all participant event data, while average per-variant size divides that total across groups.

Average event size and events per user directly increase raw data volume.

Compression reduction decreases estimated size by reducing the share of raw data that remains.

Adding variants changes the average per variant but not total volume when participants and behavior are unchanged.

Uneven traffic allocation can make actual variant-level files differ from the average.

How to Decide

Choose this if: Use total file size when estimating the volume of a combined export, dataset, or transfer.
Choose this if: Use average file size per variant only when an even participant split is a reasonable assumption.
Choose this if: Base event-size inputs on representative records rather than event-name length alone.
Choose this if: Consider a conservative and a measured compression scenario when compression performance is uncertain.
Choose this if: Check whether operational overhead outside event records needs to be added separately.
Choose this if: Recalculate when event schema, tracking coverage, participant count, or allocation strategy changes.

Assumptions

  • Comparisons assume the same participant count unless a row states otherwise.
  • Per-variant averages assume an even traffic allocation.
  • Compression is modeled as one uniform percentage applied to raw event data.
  • The estimates exclude file-format and platform-specific overhead unless it is reflected in the average event size.

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Frequently Asked Questions

Which is more useful: total file size or file size per variant?

Total size is more useful for full-experiment capacity planning. Per-variant size is useful for evenly split group-level planning.

Will adding more variants increase total event-data volume?

Not if total participants, event counts, and event sizes remain unchanged. It divides the same estimated total among more groups.

Is a smaller event payload always preferable?

It reduces estimated data volume, but the appropriate payload depends on what information the experiment needs to analyze.

Should I use a high compression estimate for planning?

Use a high reduction only when it is supported by representative data or a known workflow; otherwise compare multiple assumptions.

Why can one variant’s file be larger than the average?

That group may receive more participants or generate more events per participant than other variants.

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