由于使用培训和测试的行为不同，因此在使用Dropout时会发生这种情况.

This happens when you use Dropout, since the behaviour when training and testing are different.

在训练时，功能的百分比设置为零(在您的情况下为50％，因为您正在使用Dropout(0.5)).测试时，将使用所有功能(并适当缩放).因此，测试时的模型更加健壮-可以带来更高的测试准确性.

When training, a percentage of the features are set to zero (50% in your case since you are using Dropout(0.5)). When testing, all features are used (and are scaled appropriately). So the model at test time is more robust - and can lead to higher testing accuracies.