pspp-convert: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/pspp-convert - from package: pspp

You may install the required package with command apt-get install {package}

Error in other languages:
pspp-convert: bevel nie gevind nie
pspp-convert: comandă negăsită
pspp-convert: comando não encontrado
pspp-convert: commande introuvable
pspp-convert: command not found
pspp-convert: käsku ei ole
pspp-convert: không tìm thấy lệnh
pspp-convert: komanda nerasta
pspp-convert: Kommando nicht gefunden.
pspp-convert: kommandot finns inte
pspp-convert: komut yok
pspp-convert: nie znaleziono polecenia
pspp-convert: níor aimsíodh an t-ordú
pspp-convert: no se encontró la orden
pspp-convert: no s'ha trobat l'ordre
pspp-convert: opdracht niet gevonden
pspp-convert: parancs nem található
pspp-convert: perintah tidak ditemukan
pspp-convert: príkaz nenájdený
pspp-convert: příkaz nenalezen
pspp-convert: команда не найдена
pspp-convert: командата не е открита
pspp-convert: 命令找不到
pspp-convert: コマンドが見つかりません