Summary statistics

Monte Carlo Simulations in Python

Izzy Weber

Curriculum Manager, DataCamp

Age outcomes

What is the difference in outcomes for people in the first and fourth age quantiles? histogram of the Age variable in the simulated results

Age outcomes

print(np.quantile(df_summary["age"], 0.25))
print(np.quantile(df_summary["age"], 0.75))

39.78584463094688
57.52092642086441

Age outcomes

age_q25 = np.quantile(df_summary["age"], 0.25)
age_q75 = np.quantile(df_summary["age"], 0.75)


mean_age_q75_outcome = np.mean(df_summary[df_summary["age"] > age_q75]["predicted_y"]) 
mean_age_q25_outcome = np.mean(df_summary[df_summary["age"] < age_q25]["predicted_y"])


mean_age_q75_outcome - mean_age_q25_outcome

34.09429663553621

Outcome differences based on age and bmi

What is the difference in outcomes for people in the first and fourth quantiles of bmi and age?
What is the 95 percent confidence interval and standard deviation for this difference?

Outcome differences based on age and bmi

y_diffs = []
for i in range(1000):
    simulation_results = st.multivariate_normal.rvs(mean=mean_dia, size=1000, cov=cov_dia)
    df_results = pd.DataFrame(simulation_results, columns=["age", "bmi", "bp", "tc", "ldl", 
                                                           "hdl", "tch", "ltg", "glu"])

    predicted_y = regr_model.predict(df_results)
    df_y = pd.DataFrame(predicted_y, columns=["predicted_y"])
    df_sum = pd.concat([df_results, df_y], axis=1)

    age_q25 = np.quantile(df_sum["age"], 0.25)
    age_q75 = np.quantile(df_sum["age"], 0.75)
    bmi_q25 = np.quantile(df_sum["bmi"], 0.25)
    bmi_q75 = np.quantile(df_sum["bmi"], 0.75)

    q75_outcome = np.mean(df_sum[(df_sum["bmi"] > bmi_q75) & (df_sum["age"] > age_q75)]["predicted_y"]) 
    q25_outcome = np.mean(df_sum[(df_sum["bmi"] < bmi_q25) & (df_sum["age"] < age_q25)]["predicted_y"])

    y_diff = q75_outcome - q25_outcome 
    y_diffs.append(y_diff)

Outcome differences based on age and bmi

Mean:
```
np.mean(y_diffs)
```

132.4948511247819

95% confidence interval:
```
np.quantile(y_diffs,0.025)
```

120.73340800299707

np.quantile(y_diffs,0.975)

144.1344994507557

Standard deviation:
```
np.std(y_diffs)
```

5.9322225537128

Histogram of the results:
```
sns.histplot(y_diffs)
```

Let's practice!

Monte Carlo Simulations in Python