Skype has a survey that pops up after a call called "How was the call quality?"  The frequency that users receive this survey can be changed.  

This feature is described in a number of articles:
Rate my Call in Skype for Business Server 2015

Rate My Call in Skype for Business 2015

Jens Trier Rasmussen says, "The RateMyCallDisplayPercentage parameter controls how often the form is shown. You should interpret it as each X times, i.e. if the RateMyCallDisplayPercentage is set to 10 the form will be shown each 10th call."

Based on this, using the PowerShell "Set-CsClientPolicy -Identity Global -RateMyCallDisplayPercentage 1" should have increased the frequency of surveys.  This did not happen.

Based on a Microsoft Premiere Support case, for Skype for Business Online users, they should be configured to use the CPCPstnPreviewRateMyCAllClientPolicy.  That policy has RateMyCallDisplayPercentage = 100.

Import-Module "C:\Program Files\Common Files\Skype for Business Online\Modules\SkypeOnlineConnector\SkypeOnlineConnector.psd1"
$CSSession = New-CsOnlineSession -OverrideAdminDomain
Import-PSSession $CSSession -AllowClobber
Grant-CsClientPolicy -Identity -PolicyName CPCPstnPreviewRateMyCallClientPolicy
Remove-PSSession $CSSession