Neither (i) | A only (ii) | B only (iii) | Both – A first (iv) | Both – B first (v) | |
---|---|---|---|---|---|
Time 0 | 10000 | 0 | 0 | 0 | 0 |
Start using A | 250 i → ii | ||||
Start using B | 500 i → iii | ||||
Time 1 | 10000 − 250 − 500 = 9250 | 250 | 500 | 0 | 0 |
Start using A | 231 i → ii | 13 iii → v | |||
Start using B | 463 i → iii | 13 ii → iv | |||
Time 2 | 9250 − 231 − 463 = 8556 | 250 + 231 − 13 = 469 | 500 + 463 − 13 = 950 | 13 | 13 |
Start using A | 214 i → ii | 24 iii → v | |||
Start using B | 428 i → iii | 23 ii → iv | |||
Time 3 | 8556 − 214 − 428 = 7915 | 469 + 214 − 23 = 659 | 950 + 428 − 24 = 1354 | 13 + 23 = 36 | 13 + 24 = 36 |
Start using A | 198 i → ii | 34 iii → v | |||
Start using B | 396 i → iii | 33 ii → iv | |||
Time 4 | 7915 − 198 − 396 = 7321 | 659 + 198 − 33 = 824 | 1354 + 396 − 34 = 1716 | 36 + 33 = 69 | 36 + 34 = 70 |
P1: Proportion who start B among A first users | 69/(824 + 69) | =0.08 | |||
P2: Proportion who start B among others | (1716 + 70)/(7321 + 1716 + 70) | =0.20 | |||
P3: Proportion who start B among never A users | 1716/(7321 + 1716) | =0.19 | |||
OR1 as defined in (using P1 and P2) | (0.08/(1-0.08))/(0.20/(1-0.20)) | =0.34 | |||
OR2 as defined in (using P1 and P3) | (0.08/(1-0.08))/(0.19/(1-0.19)) | =0.36 | |||
RR stratified by period (using columns i and ii) | Period 1–2 | (13/250)/(463/9250) | =1 | ||
Period 2–3 | (23/469)/(428/8556) | =1 | |||
Period 3–4 | (33/659)/(396/7915) | =1 |