**The data is mostly clean, with no impossible values and no format problems. The issues are missing values, a few suspicious clusters and ceilings, and one odd age/level combination.** All figures below come from my profiling queries (steps 0–3). **Clean checks** - **Keys and duplicates:** `Student_ID` has 4,500 distinct values across 4,500 rows, with no nulls. Every ID is 11 characters, running from STU_2024000 to STU_2028499, so the format is consistent. One of my format-flag checks counted all 4,500 rows as "odd". Since lengths and the range are uniform, I think my test pattern was wrong, not the data, but I didn't re-verify it. - **Categoricals:** All categorical columns have 0 nulls. Labels look standardised, with no spelling or case variants. For example, Gender has Female, Male, Non-Binary and Prefer not to say, and Late_Night_Usage is a proper boolean. - **Ranges:** All numeric columns are within plausible bounds. | Column | Range | |---|---| | Age | 15–26 | | Daily_Usage_Hours | 0.9–14.0 | | Weekend_Extra_Hours | 0–4.5 | | Sleep_Duration_Hours | 3.0–10.5 | | Sleep_Quality_Score | 1–5 | | Mental_Health_Index | 32–98 | | Perceived_Stress_Score | 0–40 | | Academic_Performance_GPA | 1.9–4.0 | - **Logical consistency:** No row has daily usage plus sleep above 20 hours. No postgraduate is aged 20 or under, and no undergraduate is aged 16 or under. - **Mixed units:** I found no sign of them. Each measure sits in one consistent scale, such as hours, a 1–5 score, a 0–40 stress score, or a GPA on a 4.0 scale. **Issues worth flagging** 1. **Missing values in two measures.** - `Perceived_Stress_Score` is null in 46 rows, with 4,454 non-null. - `Academic_Performance_GPA` is null in 85 rows, with 4,415 non-null. - Any stress or GPA analysis silently drops these rows. 2. **Ceiling effect in GPA.** 353 students (about 7.8%) have exactly 4.0, which is the maximum. This suggests the values were capped or clipped and understates the true spread at the top. 3. **Suspicious clusters in the stress score.** - 87 rows have a stress score of exactly 0, which is implausible for a perceived-stress scale and may be a placeholder for "missing". - 8 rows sit at exactly 40, the scale maximum. 4. **Possible clipping in other measures.** - 55 students have daily usage of exactly 14.0, the maximum. - 11 students sleep exactly 3.0 hours, the minimum. - 1 student sleeps exactly 10.5 hours, the maximum. - These are potential censoring points, not necessarily errors. 5. **Extreme usage.** 126 students report 12 or more hours a day. That is possible but extreme, so treat it as outliers. Daily usage averages about 5.3 hours with a standard deviation of about 2.6. 6. **Age/level mismatch.** 156 students are labelled High School but are aged 19 or older. That is unusual, though it could be real, for example in extended schooling systems. 7. **Class imbalance.** This is not an error, but it limits comparisons. - Overall_Impact: Beneficial 3,681, Neutral 654, Negative 165. - Device_Type: Smartphone 3,775 of 4,500. - Academic_Level: Postgraduate only 246. - Primary_Platform: LinkedIn only 96. - Subgroup results for the smaller groups will be noisy. **Recommendation:** Decide how to treat the zero stress scores, either as missing or valid. Keep the 4.0 GPA ceiling in mind when interpreting GPA, and check whether the 19+ High School cases reflect a labelling convention.