We are suggesting changes to one matched half and leaving the other half alone so your own till numbers tell us what happened, rather than us guessing. This week, consider the suggestions in Arm A and the solo section, and leave every Arm B price exactly as it is.
These are the suggested first changes. On the cautious basis they are worth about £40 a year in total. That figure is not the price rise multiplied by today's units: VAT comes off first, then the cost of the stock, then the margin on the units we expect to stop selling.
| Line | Till code | Current | This week | Sold per day |
|---|---|---|---|---|
| Apple juice family packThis is a first step. A second step may follow after the read. | 9900000000008 | £2.90 | £3.00 | 3.27 |
| Cheddar slices small packThis is a first step. A second step may follow after the read. | 9900000000015 | £2.79 | £2.89 | 2.85 |
| Milk chocolate small packThis is a first step. A second step may follow after the read. | 9900000000009 | £1.13 | £1.20 | 2.23 |
| Tomato soup small packThis is a first step. A second step may follow after the read. | 9900000000003 | £3.18 | £3.28 | 4.08 |
| Baked beans family packThis is a first step. A second step may follow after the read. | 9900000000004 | £2.00 | £2.10 | 1.60 |
| Orange drink small packThis is a first step. A second step may follow after the read. | 9900000000006 | £1.01 | £1.07 | 2.33 |
Arm B is the held comparison. Changing even one of these prices weakens the read. Holding it back leaves about £46 a year on the table for now, on the same cautious basis.
| Line | Till code | Current | This week | Sold per day |
|---|---|---|---|---|
| Long grain rice family pack | 9900000000002 | £3.07 | Leave unchanged | 4.55 |
| Baked beans small pack | 9900000000020 | £1.00 | Leave unchanged | 3.60 |
| Mint sweets small pack | 9900000000011 | £3.17 | Leave unchanged | 4.00 |
| Still water small pack | 9900000000005 | £1.44 | Leave unchanged | 3.78 |
| Natural yoghurt small pack | 9900000000014 | £1.42 | Leave unchanged | 2.97 |
Each line here is too large to hide inside an arm, so it gets its own read on 3 November 2026. A suggestion is still the owner's call.
| Line | Till code | Current | This week | Sold per day |
|---|---|---|---|---|
| Apple juice small packThis is a first step. A second step may follow after the read. | 9900000000024 | £1.49 | £1.58 | 2.73 |
Apple juice small pack: 2.73 units per day, about 153 units across 56 days, with a noise floor of about ±11.4%. This can only support a conclusion about this line if the change is larger than that noise floor. Smaller movement cannot be separated from ordinary sales noise.
We will compare 56 days before and after the changes. The held arm helps us judge whether the changed arm moved differently from ordinary trading. It does not promise an outcome, and it does not identify customer response before the read.
Arm A before-and-after: 16.36 units per day, about 916 units across 56 days, with a noise floor of about ±4.7%. This is the before-and-after floor for this arm, not the threshold for comparing Arm A with Arm B. It cannot tell us what happened on each line.
Arm B before-and-after: 18.90 units per day, about 1,058 units across 56 days, with a noise floor of about ±4.3%. This is the before-and-after floor for this arm, not the threshold for comparing Arm A with Arm B. It cannot tell us what happened on each line.
Arm A against Arm B: the combined one-standard-error comparison floor is about ±6.4%. About ±12.5% is a rough 95% reference before overdispersion or department confounding, not a conclusion threshold. We will read the result with those limits rather than treating one standard error as proof.
Residual arm difference: yearly value 13.0%; daily units 13.4%; department coverage 4 in Arm A and 4 in Arm B, with 4 departments shared. These are recorded limits, not hidden precision.
0 lines fell below one unit per day. Together their yearly gap is £0 at current volumes, before any customer response. They are worth doing later and are not being ignored. An eight-week read is too noisy to judge them honestly in this batch. At the boundary, one sale a day gives 56 units in the window and about ±18.9% noise on a before-and-after ratio, so it cannot support a line-level conclusion.
0 lines, with a yearly gap of £0 at current volumes, before any customer response, carry a different-product warning. They are not safe to put into this experiment until the matched names have been checked, so they are disclosed here but not allocated to either arm.