Statistical significance considers the first and third of these concerns. The middle one, bias, cannot be detected by mathematical deductive logic: it needs detailed information on the way the sample was chosen. This is dealt with in the notes on bias.
A HEIC file is a raster image saved in the High Efficiency Image Format (HEIF), a lossy compressed format. It may contain still images, image collections, image bursts, or image sequences, along with metadata that describes each image. HEIC files may also appear as .HEIF files.
Yeah, we don't know either. The reality is that they are HEIF files, but can have a file name (extension) of either .heif or heic. And with iOS 11 Apple's new image format uses the .heic file format (videos have an .hevc extension). Either way, here's how to deal with those HEIC files you may be receiving. If you've started receiving files with the .heic extension you may be wondering just what the heck HEIC files are.