Variance Estimation Toolkit (VET)

Disclaimer: This is not an officially supported Google product.

Overview

This repository contains code for generating simulated item/response distributions of various shapes, and measuring the p-value of comparisons between those distributions. Its primary use case is facilitating the power analysis of human ratings for comparing two versions of an AI system. It has three main components:

1. parameterized_sample.py Generates a large (typically 1000) number of samples of simulated output from three sources: a pool of human annotators and two machines, using known probability distributions.
2. response_resampler.py Estimates p-values directly on the data generated by parameterized_sample.py and also via resampling on the first sampled set of data from parameterized_sample.py It then compares the results on the generated data and resampled data, where the resampled estimates are the kinds of estimates available to investigators under normal experiment conditions, and the estimates from parameterized_sample.py are a more accurate value of the p-value under a null hypothesis based on the actual distributions that generated the data. response_resampler.py can be run in parallel, to save time.

Usage

Example usage for response sample generation:

python parameterized_sample.py --exp_dir=/data_dir/path --distortion=.02

Where:

--exp_dir is the file path where the experiment input and output data are located.

--generator is the type of random sample generator. Right now it supports either normal distribution generator (ALT_DISTR_GEN) or Likert normal distribution generator (TOXICITY_DISTR_GEN). A Likert normal distribution here refers to a normal distribution with the probability value thresholded to the closest (equispaced) interval corresponding to the Likert scale normalized between 0 and 1.

--distortion is a floating point number controlling the amount of distribution generation error in the second machine sample distribution relative to the human sample distribution.

--n_items is the number of items per response set. Each item is assumed to have its own distribution.

--k_responses is the number of responses per item. They can be annotators responses for human results or machine responses for machine results.

--num_samples is the number of sample sets per experiment. Each set contains n_items * k_responses samples for human, machine1 and machine2 results.

--use_pickle decides whether to save the sample data in pickle format. When set to false, the samples are saved in json format, which is more readable but less efficient in storage space.

Example usage for computing metrics over the generated samples:

python response_resampler.py --exp_dir=/path/to/experiment/ --input_response_file=input_file_prefix --config_file=config.csv --line_num=45

Where:

--exp_dir is the path to the input/output files for the experiment.

--input_response_file is the name of the input file. The output file name is generated based on the input file name and the experiment config.

--line_num is the number of config line to run. When running in parallel, each resampler job can do the processing according to one line of the experiment config.

--config_file is the name of the config csv file located in <exp_dir>/config/<config_file>.

--n_items and --k_responses are similar to the flags in parameterized_sample.py. They can be redefined for resampling.