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Databricks Machine Learning Associate Exam - Topic 1 Question 34 Discussion

Posted by Marshall on Aug 12, 2025 at 08:01 AM

A data scientist wants to efficiently tune the hyperparameters of a scikit-learn model. They elect to use the Hyperopt library's fmin operation to facilitate this process. Unfortunately, the final model is not very accurate. The data scientist suspects that there is an issue with the objective_function being passed as an argument to fmin.

They use the following code block to create the objective_function:

Which of the following changes does the data scientist need to make to their objective_function in order to produce a more accurate model?

Suggested Answer: D

When using the Hyperopt library with fmin, the goal is to find the minimum of the objective function. Since you are using cross_val_score to calculate the R2 score which is a measure of the proportion of the variance for a dependent variable that's explained by an independent variable(s) in a regression model, higher values are better. However, fmin seeks to minimize the objective function, so to align with fmin's goal, you should return the negative of the R2 score (-r2). This way, by minimizing the negative R2, fmin is effectively maximizing the R2 score, which can lead to a more accurate model.

Reference

Hyperopt Documentation: http://hyperopt.github.io/hyperopt/

Scikit-Learn documentation on model evaluation: https://scikit-learn.org/stable/modules/model_evaluation.html


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14 comments · newest first
LO
Lorrine 10 months ago
Not sure about removing the mean operation, that sounds risky.
DI
Diane 10 months ago
I think replacing r2 with -r2 makes sense for minimization.
DE
Denae 10 months ago
Adding a test set validation process is crucial!
SH
Sherill 10 months ago
Wait, can you really just swap fmin for fmax? That seems odd!
AR
Arlie 10 months ago
Random state is important for reproducibility, but not the main issue here.
MA
Marleen 11 months ago
I vaguely recall something about random_state affecting reproducibility, but I’m not convinced it would directly improve the model's accuracy in this case.
AL
Allene 11 months ago
I feel like we practiced a question similar to this where we had to adjust the return value. Replacing r2 with -r2 seems like it could be a good move to maximize the score.
CE
Celia 11 months ago
I'm not entirely sure, but I think removing the mean operation around cross_val_score might be necessary. It could be skewing the results somehow.
LA
Larue 11 months ago
I remember we discussed the importance of validation sets in tuning hyperparameters. Adding a test set validation process could really help improve accuracy.
AB
Abraham 12 months ago
Hmm, this is an interesting challenge. I think the key might be to replace the r2 return value with -r2. That could help the optimization process find a more accurate model. I'll give that a try and see how it goes.
PE
Pearly 12 months ago
I'm a bit confused by this one. There are a few different options, and I'm not sure which one is the right approach. I'll need to carefully read through the question and the code to try to figure out the best solution.
YU
Yuette 12 months ago
Alright, this is a good one. I think the issue might be with the mean operation wrapping the cross_val_score. I'll need to explore that a bit more to see if that's the root of the problem.
KI
Kiley 1 year ago
Okay, let's see here. The key seems to be identifying what's wrong with the objective function that's being passed to fmin. I'll need to consider the different options and think through the implications of each.
IN
Inocencia 1 year ago
Hmm, this looks like a tricky one. I'll need to carefully review the code and think through the potential issues with the objective function.
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