We have recently integrated Amplitude analytics and have more recently been testing Amplitude Experiments on our website. For our first test experiment, the ratio between assignment and exposure is roughly 2:1, so there is double the amount of assignments as there is exposures and we don’t know why that is?

We also checked in Pathfinder and could see the following problem: Sometimes exposures seem to occur before the assignment event, is that an issue?

We included the Amplitude browser and experiment sdks via the npm modules @amplitude/experiment-js-client and @amplitude/analytics-browser We then initialize the experiment sdk like so:

  private _experiment = Experiment.initializeWithAmplitudeAnalytics(
    environment.amplitudeDeploymentKey,
    { fetchOnStart: true }
  );

as well as the browser SDK:

amplitude.init(environment.amplitudeApiKey, { defaultTracking: true });

and here is the code that checks the variant with additional experiment.start() call just in case:

  hasVariantValue(
    experimentFlag: string,
    variantValue: string
  ): Promise<boolean> {
    return new Promise((resolve, reject) => {
      this.initExperiments().then(
        () => {
          const variant = this._experiment.variant(experimentFlag);
          resolve(variant.value === variantValue);
        },
        (err) => {
          reject(err);
        }
      );
    });
  }

  initExperiments(): Promise<boolean> {
    if (this._initialized) {
      return Promise.resolve(true);
    }

    return new Promise((resolve, reject) => {
      this._experiment.start().then(
        () => {
          this._initialized = true;
          resolve(true);
        },
        (err) => {
          reject(err);
        }
      );
    });
  }

and is then used like so:

const amplitude = AmplitudeService.getInstance();  
amplitude
    .hasVariantValue('alt-title-searchbox', 'treatment')
    .then((active) => {
      console.debug('lamplitude] split test active = ', active);
      if (active) { /* split test active */ }
     });

We do not set any additional device or user ids.