Data folder: /home/hatch/workspace/maineblock-products/data 

Step 1. The sample on the announcement basis
Events in the frozen file: 1104. Events with a standardized surprise of exactly zero, set aside: 4. Sample carried: 1100 events from 46 filers.
Beats: 658 (59.8 percent). Misses: 442.

Step 2. Group means and the Welch two-sample test
Beats: mean abnormal return +51.1 basis points over days -1 to +1 (n = 658).
Misses: mean abnormal return -42.2 basis points (n = 442).
Difference: +93.3 basis points. Welch t = 2.452 on 870.0 degrees of freedom, p = 0.014.
Standard error of the difference: 38 basis points.

Step 3. Effect size, standardized
Pooled within-group standard deviation of the three-day abnormal return: 605 basis points.
Standardized difference: 0.154 of a standard deviation.

Step 4. Calendar-time check
Calendar quarters carrying both groups: 25. Mean quarterly spread +62.7 basis points; one-sample t = 1.528, p = 0.140.

Step 5. Permutation check (R stream, seed 20261020)
Shuffles at least as extreme as the observed +93.3 basis points: 126 of 10,000. Permutation p = 0.0127, which prints as 0.013.

Step 6. Construction split
Tagged quarters: 880 events; difference +99.5 basis points; t = 2.363, p = 0.018.
Derived (fiscal Q4) quarters: 220 events; difference +70.1 basis points; t = 0.792, p = 0.430.

Step 7. The spread net of costs
Gross difference +93.3 basis points; two legs at 25 basis points a round trip = 50 basis points; net +43.3 basis points an event.

Part B. Solution to the R companion lane: the two halves of the sample
First half (2019-02-14 to 2022-02-10): 550 events, 353 beats; difference +111.0 basis points; t = 2.264, p = 0.024.
Second half (2022-02-17 to 2025-02-11): 550 events, 305 beats; difference +90.9 basis points; t = 1.585, p = 0.114.

Chapter 11 lab complete.
